Prepared by İsmail KURNAZ
ANKARA-2007
GAZI UNIVERSITY
EDUCATION SCIENCE INSTITUTE
GRAPHIC EDUCATION DEPARTMENT
GRAPHIC DESIGN COMPUTER
Lecturer
Prof. Ahmet ATAN
ANKARA - 2007
CONTENTS
INTRODUCTION.. 1
COMPUTER HARDWARE.. 1
Mother Board. 1
Central Processing Unit 2
Random Access Memory (RAM) 4
Graphic Card. 5
Hard Disc. 6
SOFTWARE.. 6
Resolution. 7
Image Formats. 8
USAGE OF MEMORY.. 12
Compression of the Pictures. 13
Printing Graphic Design. 17
CONCLUSION and SUGGESTION.. 17
REFERENCES. 19
INTRODUCTION
This work try to explain to the students who studies on graphic design ‘Which computer system requirements they need?’ Nowadays the solutions of graphic design implement on computer systems. First of all for preparing, modifying, rendering graphic design or to run graphic design software effiency is needed effective computer system. Design issues like as size, number of colour, resolution must be supported by the computer system.
COMPUTER HARDWARE
The devices like as mother board, central processing unit (CPU), random access memory (RAM), graphics card, hard disc affect to prepare graphic design and the quality of the solution.
Mother Board
Mother board which consists of all the devices computer system is an electronic device. It is made by fibreglass. CPU socket, RAM slots, BIOS, expanding slots and other ports are on the mother board.
Mother board is a component that most effective device for determine the ability of the computer system. The electronic components on mother board determine;
Which CPU?
Maximum capacity of the memory?
Device speed
Which new technology supported and etc.
Mother boards front side bus (FSB) and the expansion slot which used by the graphic card affect the graphic design. Digital data while transmitting between CPU, RAM, graphic card, hard disc uses mother board bus. If the bandwith of data bus is large, big-sized data can transmit fast. Graphic design files are big-sized files. So they need large bandwith. Graphic design operations need 800 MHz FSB at least. (HENKOĞLU 2005)
Graphic design operations implement graphic card of computer system. The slots which used by graphic card affects the graphic design. Graphic cards use AGP (Accelerated Graphics Port) or PCI Express expansion slots. Table 1 shows the speed of slots.
Central Processing Unit
CPU which provides computer parts working, control data communication and process the data is an electronic device. CPU can implement number of process per unit of a time is called as CPU velocity. A million processes in a second defines as Mhz (Megahertz). Nowadays CPU can implement billion processes in a second (GHz - GigaHertz). The parts of CPU core and cache memory determine the velocity of CPU.
Core is a part of CPU that executes the instructions. It is known as an execution unit. The classification of CPU as P4, P3, Celeron is caused by core. P4 has got fastest core.
The data which comes from system memory can’t be operated in CPU velocity. Thats why CPU has got fast memory ICs. Cache memory which can temprorary save processing data is high level fast memory. Cache memory has got two parts: L1 (Level 1) and L2 (Level 2). At first CPU searches the data L1 cache memory. If data is not found, then CPU search the data L2 cache memory. If no exist, it is searched RAM and virtual memory (a part of hard disc). Cache memory run as fast as CPU. (AKELEY 1989)
High level quality video and audio, database applications must be needed lots of data processes. This type of data can be process by two or more CPUs. (BORDEN 1989) But it is so expensive. Instead of this way Hyper Threading and Dual Core technologies are developped for processing high level data like as video, graphics, database applications. A HT CPU can process data of two independent programs at the same time. HT technology needs the following issues
Mother board supporting
System BIOS supporting
Operating System supporting
For example HT CPU can not work in Windows 2000 Professional operating system. HT CPU needs at least Windows XP operating system.
Figure 1. Running processes with HT CPU and non-HT CPU
Dual Core CPUs have got two cores. At the same time two core work and two process run. In Figure 2 a dual core CPU run two processes in two pipelined data bus. The other CPU which is HT and dual core can run four processes in two pipelined data bus. (WHITE ve DOWNS 2005)
Figure 2. Running processes with Dual Core CPU and Dual Core HT CPU
Random Access Memory (RAM)
RAM which save the data that waiting for process and provide fast access is an electronic device. The list of programs which will be executed by CPU save in RAM. RAM must be more memory capacity for saving lots of programmes. Files of graphic design need large memory. (HOŞGÖREN ve KARAKAYA 2005).
Another factor that affects the performance of the running is the velocity of RAM while using the system data bus. It is called as working frequency in RAM.
Figure 3 shows the communication of devices input/output, hard disc, RAM, CPU.
Figure 3. Communication between CPU and RAM
Graphic Card
Graphic card is an extended card that output signal of data processing in CPU converts the analog signal for producing an image to the monitor. Graphic cards attach to the mother board by expansion slots (AGP, PCI ex.). Basic components of the graphics cards are graphic processor (GPU), video RAM, digital to analog convertor (RAMDAC) and z-buffer. (ÖZGÜLER 2005).
Graphic processor (GPU) is a chip that implement image calculation and image operations in graphic card. GPU makes easily CPU working by processing images.
Video RAM which saved calculation result of the image is a memory. It works like as the system memory. Video RAM take the data from GPU and save it. Large sized memory increases the performance of the graphic card. If it is wanted high resolution and quality image, big sized video RAM must be used.
Digital to analog convertor (RAMDAC) sends the digital signals to the monitor output of graphic card by converting them to the analog signals. RAMDAC scans video RAM in a second many times. Then it takes data consist of digital signal and convert it to the analog signal for display on monitor. The converting data frequency and transmitting time of RAMDAC determine the velocity of display refresh time. This velocity measures as Hz. If the display refresh time sets 75 Hz in monitor, image refreshes 75 times in a second.
2d images have got two dimensions as x horizontal, y vertical. 3d images have got another dimension z depth. Z-buffer provides to show 3d images. Depth of data saves in this buffer memory. Graphic cards for implementing 3d images use z-buffer memory. 3d graphic card must have z-buffer.
Figure 4. Graphics card running
Hard Disc
The storage unit of the computer system is hard disc. Operating system that provides to run computer system, application software and user files save in hard disc. Files of graphic design are big-sized. So computer system using for graphic design must have big-sized hard disc.
SOFTWARE
To use hardware it is needed application software for every aim. For example for writing Microsoft Word, for listening WinAmp, for preparing presentation Microsoft PowerPoint. Graphic design computers need software for preparing effective graphics. So vector based drawing software and pixcel based drawing software must be installed to GDC.
Pixcel is the smallest unit of the image. It is square. Digital images occur lots of pixcels. Pixcel haven’t got any height or width dimensions. Pixcel based drawing software occurs graphic design by using pixcel. But if the graphic scales, graphic is disturbed because of pixcel size. So while preparing the graphic design using pixcel based software, document size must be set as possible as real measurements. Adobe Photoshop, Painter, Paintshop Pro, Gimp, Fireworks run as pixcel based drawing software.
Vector based drawing software save in memory all of the graphic values (colour, effects, etc.) from beginning to the end as binary numbers. If the graphic design is scaled, binary numbers change to the setting value. So image doesn’t disturb. And also file size of vector based drawing software is smaller then pixcel based drawing software. Illustrator, Freehand, CorelDraw, Flash run as vector based drawing software. (SANCHEZ and CANTON 1993)
Resolution
The controlable point producing all colours on the image is called pixcel. Resolution is the number of pixcels seen on the screen. When the resolution is 800´600 for example, it means that it is 800 pixcels horizontal and 600 pixcels vertical. The quality of the image increases as the resolution increases. The pixcel value doesn’t change when the resolution value changes. When the resolution is increased, the need of memory increases. (FRASER 2005)
Figure 5. Image area for resolution
Resolution can also be defined as the density of pixcel of a picture, PPI (pixcel per inches) that is the number of pixcels in 1 inch (1 inch = 2.54 cm).
The depth of the colour is the colour quantity a pixcel gets. When the depth increases the number of the colours each pixcel gets is also increases. The increase in the variety of the colours make the pictures more real. The colours in the pixcels are the mixture of red, gren and blue.
As the colour depth increases the data quantity of the pixcels increases. This increase also increases the data quantity to be processed by the image processor and needs more image memory.
Interlacing is a technique which was developed to produce image in high resolution. While the image is being refreshed, only the half of the screen is refreshed each time. First the odd numbered then the even numbered lines are refreshed which leads to a high resolution speed. The interlacing technique is compulsory when screening especially big dimensioned files and animations. (FOLEY 1990)
Table 2. Supporting display interfaces of resolution values
Image Formats
The programmes work through file trading in desktop broadcasting. To use a graphic written with a pixcel or vector based software, it should be made independent from the programme and be saved in specific formats. Image formats are usually used to make graphic files occupy less areas on the hard discs. (ENGLAND 2000)
PICT
The PICT format is a file format which is used and shared by all programmes. When moved to an application programme the picture information is included on the page. Even when the image is deleted from the disc, the printer doesn’t look for the PICT file when printing the page.
EPS
The EPS format is supported by nearly all drawing and page designing programmes. When saving a colored EPS document, it should be transmitted to CMYK mode to prevent probable printing problems.
In addition EPS, is a format which transmits vectoral programmes (Illustrator and Freehand) to page designing programmes. If the vectoral files are not saved in EPS format, design and picture programmes can not take them in their files.
TIFFThe TIFF format is an inter-computer common file format. They are supported by all programmes. The files saved in this format makes it possible to diminish or change the image and background colours when they are taken into an application programme page. For example, an image or logo which will be used in different colours may be changed by saving it in TIFF format.
PNG
PNG Portable Network Graphics format has no patent. PNG uses Wave Table compression method without any loss. Nowadays, the aim is to move the real colour and transparent information included in the quality of the picture to the internet. The transparency information is saved in the alfa channel in PNG files. The lined-up uploading is also possible. Also, different filtering algorithms can be used before compression for compressing.
GIF
GIF (Graphics Interchange Format) is an 8-bit-per-pixcel bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.
The format uses a palette of up to 256 distinct colors from the 24-bit RGB color space. It also supports animations and allows a separate palette of 256 colors for each frame. The color limitation makes the GIF format unsuitable for reproducing color photographs and other images with continuous color, but it is well-suited for more simple images such as graphics or logos with solid areas of color.
GIF images are compressed using the LZW lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985. The controversy over the patent licensing agreement between the patent proprietor, Unisys, and CompuServe in 1994 led to the development of the PNG (Portable Network Graphics) standard.
JPEG In computing, JPEG is a commonly used standard method of compression for photographic images. The name JPEG stands for Joint Photographic Experts Group, the name of the committee who created the standard. The group was organized in 1986, issuing a standard in 1992 which was approved in 1994 as ISO 10918-1. JPEG should not be confused with MPEG (Moving Picture Experts Group) which produces compression schemes for video.
JPEG itself specifies both the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, and the file format used to contain that stream. The compression method is usually lossy compression, meaning that some visual quality is lost in the process, although there are variations on the standard baseline JPEG which are lossless. There is also a "progressive" format, in which data is compressed in multiple passes of progressively higher detail. This is ideal for large images that will be displayed whilst downloading over a slow connection, allowing a reasonable preview before all the data has been retrieved. However, progressive JPEGs are not as widely supported.
Image files that employ JPEG compression are commonly called "JPEG files". The most common file extension for this format is jpg, though jpeg, jpe, jfif and jif are also used. It is also possible for JPEG data to be embedded in other file types, such as TIFF format images.
JPEG/JFIF is the format most used for storing and transmitting photographs on the World Wide Web. For this application, it is preferred to formats such as GIF, which has a limit of 256 distinct colors that is insufficient for color photographs, and PNG, which produces much larger image files for this type of image. The JPEG compression algorithm is not as well suited for line drawings and other textual or iconic graphics, and thus the PNG and GIF formats are preferred for these types of images.
BMP
BMP or DIB (device-independent bitmap) is a bitmapped graphics format used internally by the Microsoft Windows and OS/2 graphics subsystem (GDI), and used commonly as a simple graphics file format on those platforms.
Images are generally stored with a color depth of 2 (1-bit), 16 (4-bit), 256 (8-bit), 65,536 (16-bit), or 16.7 million (24-bit) colors (the bits represent the bits per pixcel). 8-bit images can also be grayscale instead of indexed color. An alpha channel (for transparency) may be stored in a separate file, where it is similar to a greyscale image. A 32-bit version with integrated alpha channel has been introduced with Windows XP and is used within its logon and theme system; it has yet to gain wide support in image editing software but has been supported in Adobe Photoshop since version 7 and Macromedia Flash since version MX 2004.
PSDThe PSD (Photoshop Document) format stores an image with support for most imaging options available in Photoshop. These include layers with masks, color spaces, ICC profiles, transparency, text, alpha channels & spot colors, Clipping paths, and duotone settings. This is in contrast to many other file formats (e.g. EPS or GIF) that restrict content to provide streamlined, predicatable functionality. Photoshop's popularity means that the PSD format is widely used, and it is supported to some extent by most competing software.
USAGE OF MEMORY
Number of colour, size, resolution and image format affect the size of graphic design in memory. The smallest memory capacity unit is bit. Table 3 shows the memory capacity units.
Size of graphic files decrease by using image format as JPEG, GIF. But after the compress operation it is difficult to modify graphic design. Table 4 shows memory capacity values according to resolution and image format.
Table 4. File size of image formats for resolution
Resolution
420 KB
Compression of the Pictures
Compress is a memory decrease method without disturbing basic structure of graphic design by decreasing repeating data. JPEG (Joint Photographic Experts Group) is a one of the compression way. JPEG is based on no transmitting the same points. JPEG operation implement following phases. (PULLI 2005)
Seperating pictures to the macro blocks: Digital picture is seperated macro blocks 16 ´ 16 pixcels consist of four 8´8 pixcel blocks. Each block is called as slice.
Determining the luminance and colour values: It is determined that each pixcel luminance value (Y) and different colour values (U, V or Cb, Cr) in blocks.
Figure 7. Seperating macro blocks, and samples of slice, Y, Cb, Cr
Discrete Cosine Transform (DCT): DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. DCTs are equivalent to DFTs of roughly twice the length, operating on real data with even symmetry (since the Fourier transform of a real and even function is real and even), where in some variants the input and/or output data are shifted by half a sample. There are eight standard DCT variants, of which four are common.
The most common variant of discrete cosine transform is the type-II DCT, which is often called simply the DCT; its inverse, the type-III DCT, is correspondingly often called simply the inverse DCT or the IDCT.
Figure 8. Discrete Cosine Transform
Quantization: The human eye is fairly good at seeing small differences in brightness over a relatively large area, but not so good at distinguishing the exact strength of a high frequency brightness variation. This fact allows one to get away with greatly reducing the amount of information in the high frequency components. This is done by simply dividing each component in the frequency domain by a constant for that component, and then rounding to the nearest integer. This is the main lossy operation in the whole process. As a result of this, it is typically the case that many of the higher frequency components are rounded to zero, and many of the rest become small positive or negative numbers. For example if 55/25/10/(-7)/35/1 values quantization by 8, then result becomes 7/3/1/(-1)/4/0. If reverse quantization applies the same number result becomes 56/24/(-8)/32/0.
Figure 9. DCT basic multiplier
Scanning: The values of macro blocks which applied quantization operation are scanned vertically and zigzag ordering. Then one dimensional array consist of values is constituted.
Coding: Entropy coding is a special form of lossless data compression. It involves arranging the image components in a "zigzag" order. Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. This can be contrasted to lossy data compression, which does not allow the exact original data to be reconstructed from the compressed data. Following techniques are used for coding.
Huffman Encoding: Huffman coding uses a specific method for choosing the representation for each symbol, resulting in a prefix-free code (that is, the bit string representing some particular symbol is never a prefix of the bit string representing any other symbol) that expresses the most common characters using shorter strings of bits than are used for less common source symbols.
Example: 7 / 3 / 1 / (-1) / 4 / 0 ® 01111 / 011 / 1/ 101 / 00100 / 0
Variable Length Code (VLC): In coding theory a variable-length code is a code which maps source symbols to a variable number of bits.
Run Left Encoding (RLE): RLE is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run.
Example: Input data – 22222222288881111111 Code – 2,9 8,4 1,7
Figure 10. DCT, quantization, zigzag scanning
Printing Graphic Design
Printing is to send the digital data to the printer or plotter and to see them as a picture in a paper. To see the graphic design in a paper as same as its original copy, it must be chosen the right-sized paper for supporting the resolution value.
For example if the resolution is 2048 ´ 1536 pixcel, Picture has got 2048 pixcels horizontally and 1536 pixcels vertically. In a real colour printing 1 inch consists of 300 pixcels. So;
A graphic design in 2048 ´ 1536 resolution can be printed 17 ´ 15 cm paper sized in real colour mode.
CONCLUSION and SUGGESTION
To implement graphics with computers, computers strong in hardware and software are needed. The mainboard, CPU, RAM, graphics card and hard disc hardware of the computer should be capable of preparing graphics. The main board of the graphics designing computer should have the data bus which will realize a fast communication between the main board and the CPU, RAM and hard disc. The main board data bus speed should be minimum 800 MHz. The CPU should have HT or Dual Core Technologies and the internal cache memory capacity should be 2 MB. Graphics files have big memories. System memory should be big enough to hold the graphics files which are needed to run at the same time in its memory. The minimum system memory should be 1 GB. The graphics design computer should have the graphics processor which can make the graphics card image calculations and 2d/3D image operations, an video memory which can take a high resolution image quality, and the specification of converting the digital signals to analog signals in high screen refresh rate. The hard disc should have the minimum capacity of 80 GB since it would store large graphics files.
Vector based and pixcel based application softwares are used when developing graphics applications. The largest different between vector and pixcel graphic is; the picture is made up of pixcels in pixcel based graphics. When the picture zoomed in the pixcels becaome obvious and the Picture is spoiled. On the other hand, in vectoral graphics the Picture doesn’t disturb and the pixcels aren’t seen.
The resolution values should be specified according to the size of the graphic to be prepared. The graphics card of the computer specifies the system’s resolution ability. The lowest resolution graphic cards are 640´480 pixcel VG and the highest resolution graphic cards are 2560´2048 QSXGA.
Different file types which were produced with desktop publishing graphics application software, same common image formatsa re produced to make them run with different application software. The most common formatsa re pict, eps, png, gif, jpeg, bmp and psd. Jpeg converts the large graphic files into small files by compressing them.
The printing size of the graphic according to the screen area should be specified to protect the quality when printing thr graphic files. For this end, the graphics should be designed with the output size in mind.
To get high performance, the software and hardware should be right configurated.
REFERENCES
HENKOĞLU, T. (2005). Modern Donanım Mimarisi, Pusula Press.
2. AKELEY, K. (1989). The Silicon Graphics 4D/240GTX Superworkstation. IEEE Computer Graphics & Applications.
3. BORDEN, B.S. (1989) Graphics Processing on a Graphics Supercomputer. IEEE Computer Graphics & Applications.
4. WHITE, R. DOWNS, T. E.(2005). How Computers Work, QUE.
5. HOŞGÖREN, M. KARAKAYA, M. (2005). Donanım Mimarisi, MEB. İstanbul.
6. ÖZGÜLER, M. (2005) Bilgisayar Donanımı. Abp Press, Trabzon
7. SANCHEZ, J. CANTON, M.P. (1993). Graphics Programming Solutions. McGraw-Hill Publishing. USA.
8. FRASER, B. and others. (2005). Real World Color Management. Peachpit Press. USA.
9. FOLEY, J. and others. (1990) Computer Graphics: Principle and Practice. Addison-Wesley Publishing.
10. ENGLAND, N. (2000). Graphics Design. IEEE Computer Graphics & Applications.
11. PULLI, K. and others (2005). Designing Graphics Programming Interfaces for Mobile Devices. IEEE Computer Society.
12. BRITTAIN, D.L. (1990). Portability of Interactive Graphics Software. IEEE Computer Graphics & Applications.
ANKARA-2007
GAZI UNIVERSITY
EDUCATION SCIENCE INSTITUTE
GRAPHIC EDUCATION DEPARTMENT
GRAPHIC DESIGN COMPUTER
Lecturer
Prof. Ahmet ATAN
ANKARA - 2007
CONTENTS
INTRODUCTION.. 1
COMPUTER HARDWARE.. 1
Mother Board. 1
Central Processing Unit 2
Random Access Memory (RAM) 4
Graphic Card. 5
Hard Disc. 6
SOFTWARE.. 6
Resolution. 7
Image Formats. 8
USAGE OF MEMORY.. 12
Compression of the Pictures. 13
Printing Graphic Design. 17
CONCLUSION and SUGGESTION.. 17
REFERENCES. 19
INTRODUCTION
This work try to explain to the students who studies on graphic design ‘Which computer system requirements they need?’ Nowadays the solutions of graphic design implement on computer systems. First of all for preparing, modifying, rendering graphic design or to run graphic design software effiency is needed effective computer system. Design issues like as size, number of colour, resolution must be supported by the computer system.
COMPUTER HARDWARE
The devices like as mother board, central processing unit (CPU), random access memory (RAM), graphics card, hard disc affect to prepare graphic design and the quality of the solution.
Mother Board
Mother board which consists of all the devices computer system is an electronic device. It is made by fibreglass. CPU socket, RAM slots, BIOS, expanding slots and other ports are on the mother board.
Mother board is a component that most effective device for determine the ability of the computer system. The electronic components on mother board determine;
Which CPU?
Maximum capacity of the memory?
Device speed
Which new technology supported and etc.
Mother boards front side bus (FSB) and the expansion slot which used by the graphic card affect the graphic design. Digital data while transmitting between CPU, RAM, graphic card, hard disc uses mother board bus. If the bandwith of data bus is large, big-sized data can transmit fast. Graphic design files are big-sized files. So they need large bandwith. Graphic design operations need 800 MHz FSB at least. (HENKOĞLU 2005)
Graphic design operations implement graphic card of computer system. The slots which used by graphic card affects the graphic design. Graphic cards use AGP (Accelerated Graphics Port) or PCI Express expansion slots. Table 1 shows the speed of slots.
Central Processing Unit
CPU which provides computer parts working, control data communication and process the data is an electronic device. CPU can implement number of process per unit of a time is called as CPU velocity. A million processes in a second defines as Mhz (Megahertz). Nowadays CPU can implement billion processes in a second (GHz - GigaHertz). The parts of CPU core and cache memory determine the velocity of CPU.
Core is a part of CPU that executes the instructions. It is known as an execution unit. The classification of CPU as P4, P3, Celeron is caused by core. P4 has got fastest core.
The data which comes from system memory can’t be operated in CPU velocity. Thats why CPU has got fast memory ICs. Cache memory which can temprorary save processing data is high level fast memory. Cache memory has got two parts: L1 (Level 1) and L2 (Level 2). At first CPU searches the data L1 cache memory. If data is not found, then CPU search the data L2 cache memory. If no exist, it is searched RAM and virtual memory (a part of hard disc). Cache memory run as fast as CPU. (AKELEY 1989)
High level quality video and audio, database applications must be needed lots of data processes. This type of data can be process by two or more CPUs. (BORDEN 1989) But it is so expensive. Instead of this way Hyper Threading and Dual Core technologies are developped for processing high level data like as video, graphics, database applications. A HT CPU can process data of two independent programs at the same time. HT technology needs the following issues
Mother board supporting
System BIOS supporting
Operating System supporting
For example HT CPU can not work in Windows 2000 Professional operating system. HT CPU needs at least Windows XP operating system.
Figure 1. Running processes with HT CPU and non-HT CPU
Dual Core CPUs have got two cores. At the same time two core work and two process run. In Figure 2 a dual core CPU run two processes in two pipelined data bus. The other CPU which is HT and dual core can run four processes in two pipelined data bus. (WHITE ve DOWNS 2005)
Figure 2. Running processes with Dual Core CPU and Dual Core HT CPU
Random Access Memory (RAM)
RAM which save the data that waiting for process and provide fast access is an electronic device. The list of programs which will be executed by CPU save in RAM. RAM must be more memory capacity for saving lots of programmes. Files of graphic design need large memory. (HOŞGÖREN ve KARAKAYA 2005).
Another factor that affects the performance of the running is the velocity of RAM while using the system data bus. It is called as working frequency in RAM.
Figure 3 shows the communication of devices input/output, hard disc, RAM, CPU.
Figure 3. Communication between CPU and RAM
Graphic Card
Graphic card is an extended card that output signal of data processing in CPU converts the analog signal for producing an image to the monitor. Graphic cards attach to the mother board by expansion slots (AGP, PCI ex.). Basic components of the graphics cards are graphic processor (GPU), video RAM, digital to analog convertor (RAMDAC) and z-buffer. (ÖZGÜLER 2005).
Graphic processor (GPU) is a chip that implement image calculation and image operations in graphic card. GPU makes easily CPU working by processing images.
Video RAM which saved calculation result of the image is a memory. It works like as the system memory. Video RAM take the data from GPU and save it. Large sized memory increases the performance of the graphic card. If it is wanted high resolution and quality image, big sized video RAM must be used.
Digital to analog convertor (RAMDAC) sends the digital signals to the monitor output of graphic card by converting them to the analog signals. RAMDAC scans video RAM in a second many times. Then it takes data consist of digital signal and convert it to the analog signal for display on monitor. The converting data frequency and transmitting time of RAMDAC determine the velocity of display refresh time. This velocity measures as Hz. If the display refresh time sets 75 Hz in monitor, image refreshes 75 times in a second.
2d images have got two dimensions as x horizontal, y vertical. 3d images have got another dimension z depth. Z-buffer provides to show 3d images. Depth of data saves in this buffer memory. Graphic cards for implementing 3d images use z-buffer memory. 3d graphic card must have z-buffer.
Figure 4. Graphics card running
Hard Disc
The storage unit of the computer system is hard disc. Operating system that provides to run computer system, application software and user files save in hard disc. Files of graphic design are big-sized. So computer system using for graphic design must have big-sized hard disc.
SOFTWARE
To use hardware it is needed application software for every aim. For example for writing Microsoft Word, for listening WinAmp, for preparing presentation Microsoft PowerPoint. Graphic design computers need software for preparing effective graphics. So vector based drawing software and pixcel based drawing software must be installed to GDC.
Pixcel is the smallest unit of the image. It is square. Digital images occur lots of pixcels. Pixcel haven’t got any height or width dimensions. Pixcel based drawing software occurs graphic design by using pixcel. But if the graphic scales, graphic is disturbed because of pixcel size. So while preparing the graphic design using pixcel based software, document size must be set as possible as real measurements. Adobe Photoshop, Painter, Paintshop Pro, Gimp, Fireworks run as pixcel based drawing software.
Vector based drawing software save in memory all of the graphic values (colour, effects, etc.) from beginning to the end as binary numbers. If the graphic design is scaled, binary numbers change to the setting value. So image doesn’t disturb. And also file size of vector based drawing software is smaller then pixcel based drawing software. Illustrator, Freehand, CorelDraw, Flash run as vector based drawing software. (SANCHEZ and CANTON 1993)
Resolution
The controlable point producing all colours on the image is called pixcel. Resolution is the number of pixcels seen on the screen. When the resolution is 800´600 for example, it means that it is 800 pixcels horizontal and 600 pixcels vertical. The quality of the image increases as the resolution increases. The pixcel value doesn’t change when the resolution value changes. When the resolution is increased, the need of memory increases. (FRASER 2005)
Figure 5. Image area for resolution
Resolution can also be defined as the density of pixcel of a picture, PPI (pixcel per inches) that is the number of pixcels in 1 inch (1 inch = 2.54 cm).
The depth of the colour is the colour quantity a pixcel gets. When the depth increases the number of the colours each pixcel gets is also increases. The increase in the variety of the colours make the pictures more real. The colours in the pixcels are the mixture of red, gren and blue.
As the colour depth increases the data quantity of the pixcels increases. This increase also increases the data quantity to be processed by the image processor and needs more image memory.
Interlacing is a technique which was developed to produce image in high resolution. While the image is being refreshed, only the half of the screen is refreshed each time. First the odd numbered then the even numbered lines are refreshed which leads to a high resolution speed. The interlacing technique is compulsory when screening especially big dimensioned files and animations. (FOLEY 1990)
Table 2. Supporting display interfaces of resolution values
Image Formats
The programmes work through file trading in desktop broadcasting. To use a graphic written with a pixcel or vector based software, it should be made independent from the programme and be saved in specific formats. Image formats are usually used to make graphic files occupy less areas on the hard discs. (ENGLAND 2000)
PICT
The PICT format is a file format which is used and shared by all programmes. When moved to an application programme the picture information is included on the page. Even when the image is deleted from the disc, the printer doesn’t look for the PICT file when printing the page.
EPS
The EPS format is supported by nearly all drawing and page designing programmes. When saving a colored EPS document, it should be transmitted to CMYK mode to prevent probable printing problems.
In addition EPS, is a format which transmits vectoral programmes (Illustrator and Freehand) to page designing programmes. If the vectoral files are not saved in EPS format, design and picture programmes can not take them in their files.
TIFFThe TIFF format is an inter-computer common file format. They are supported by all programmes. The files saved in this format makes it possible to diminish or change the image and background colours when they are taken into an application programme page. For example, an image or logo which will be used in different colours may be changed by saving it in TIFF format.
PNG
PNG Portable Network Graphics format has no patent. PNG uses Wave Table compression method without any loss. Nowadays, the aim is to move the real colour and transparent information included in the quality of the picture to the internet. The transparency information is saved in the alfa channel in PNG files. The lined-up uploading is also possible. Also, different filtering algorithms can be used before compression for compressing.
GIF
GIF (Graphics Interchange Format) is an 8-bit-per-pixcel bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.
The format uses a palette of up to 256 distinct colors from the 24-bit RGB color space. It also supports animations and allows a separate palette of 256 colors for each frame. The color limitation makes the GIF format unsuitable for reproducing color photographs and other images with continuous color, but it is well-suited for more simple images such as graphics or logos with solid areas of color.
GIF images are compressed using the LZW lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985. The controversy over the patent licensing agreement between the patent proprietor, Unisys, and CompuServe in 1994 led to the development of the PNG (Portable Network Graphics) standard.
JPEG In computing, JPEG is a commonly used standard method of compression for photographic images. The name JPEG stands for Joint Photographic Experts Group, the name of the committee who created the standard. The group was organized in 1986, issuing a standard in 1992 which was approved in 1994 as ISO 10918-1. JPEG should not be confused with MPEG (Moving Picture Experts Group) which produces compression schemes for video.
JPEG itself specifies both the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, and the file format used to contain that stream. The compression method is usually lossy compression, meaning that some visual quality is lost in the process, although there are variations on the standard baseline JPEG which are lossless. There is also a "progressive" format, in which data is compressed in multiple passes of progressively higher detail. This is ideal for large images that will be displayed whilst downloading over a slow connection, allowing a reasonable preview before all the data has been retrieved. However, progressive JPEGs are not as widely supported.
Image files that employ JPEG compression are commonly called "JPEG files". The most common file extension for this format is jpg, though jpeg, jpe, jfif and jif are also used. It is also possible for JPEG data to be embedded in other file types, such as TIFF format images.
JPEG/JFIF is the format most used for storing and transmitting photographs on the World Wide Web. For this application, it is preferred to formats such as GIF, which has a limit of 256 distinct colors that is insufficient for color photographs, and PNG, which produces much larger image files for this type of image. The JPEG compression algorithm is not as well suited for line drawings and other textual or iconic graphics, and thus the PNG and GIF formats are preferred for these types of images.
BMP
BMP or DIB (device-independent bitmap) is a bitmapped graphics format used internally by the Microsoft Windows and OS/2 graphics subsystem (GDI), and used commonly as a simple graphics file format on those platforms.
Images are generally stored with a color depth of 2 (1-bit), 16 (4-bit), 256 (8-bit), 65,536 (16-bit), or 16.7 million (24-bit) colors (the bits represent the bits per pixcel). 8-bit images can also be grayscale instead of indexed color. An alpha channel (for transparency) may be stored in a separate file, where it is similar to a greyscale image. A 32-bit version with integrated alpha channel has been introduced with Windows XP and is used within its logon and theme system; it has yet to gain wide support in image editing software but has been supported in Adobe Photoshop since version 7 and Macromedia Flash since version MX 2004.
PSDThe PSD (Photoshop Document) format stores an image with support for most imaging options available in Photoshop. These include layers with masks, color spaces, ICC profiles, transparency, text, alpha channels & spot colors, Clipping paths, and duotone settings. This is in contrast to many other file formats (e.g. EPS or GIF) that restrict content to provide streamlined, predicatable functionality. Photoshop's popularity means that the PSD format is widely used, and it is supported to some extent by most competing software.
USAGE OF MEMORY
Number of colour, size, resolution and image format affect the size of graphic design in memory. The smallest memory capacity unit is bit. Table 3 shows the memory capacity units.
Size of graphic files decrease by using image format as JPEG, GIF. But after the compress operation it is difficult to modify graphic design. Table 4 shows memory capacity values according to resolution and image format.
Table 4. File size of image formats for resolution
Resolution
420 KB
Compression of the Pictures
Compress is a memory decrease method without disturbing basic structure of graphic design by decreasing repeating data. JPEG (Joint Photographic Experts Group) is a one of the compression way. JPEG is based on no transmitting the same points. JPEG operation implement following phases. (PULLI 2005)
Seperating pictures to the macro blocks: Digital picture is seperated macro blocks 16 ´ 16 pixcels consist of four 8´8 pixcel blocks. Each block is called as slice.
Determining the luminance and colour values: It is determined that each pixcel luminance value (Y) and different colour values (U, V or Cb, Cr) in blocks.
Figure 7. Seperating macro blocks, and samples of slice, Y, Cb, Cr
Discrete Cosine Transform (DCT): DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. DCTs are equivalent to DFTs of roughly twice the length, operating on real data with even symmetry (since the Fourier transform of a real and even function is real and even), where in some variants the input and/or output data are shifted by half a sample. There are eight standard DCT variants, of which four are common.
The most common variant of discrete cosine transform is the type-II DCT, which is often called simply the DCT; its inverse, the type-III DCT, is correspondingly often called simply the inverse DCT or the IDCT.
Figure 8. Discrete Cosine Transform
Quantization: The human eye is fairly good at seeing small differences in brightness over a relatively large area, but not so good at distinguishing the exact strength of a high frequency brightness variation. This fact allows one to get away with greatly reducing the amount of information in the high frequency components. This is done by simply dividing each component in the frequency domain by a constant for that component, and then rounding to the nearest integer. This is the main lossy operation in the whole process. As a result of this, it is typically the case that many of the higher frequency components are rounded to zero, and many of the rest become small positive or negative numbers. For example if 55/25/10/(-7)/35/1 values quantization by 8, then result becomes 7/3/1/(-1)/4/0. If reverse quantization applies the same number result becomes 56/24/(-8)/32/0.
Figure 9. DCT basic multiplier
Scanning: The values of macro blocks which applied quantization operation are scanned vertically and zigzag ordering. Then one dimensional array consist of values is constituted.
Coding: Entropy coding is a special form of lossless data compression. It involves arranging the image components in a "zigzag" order. Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. This can be contrasted to lossy data compression, which does not allow the exact original data to be reconstructed from the compressed data. Following techniques are used for coding.
Huffman Encoding: Huffman coding uses a specific method for choosing the representation for each symbol, resulting in a prefix-free code (that is, the bit string representing some particular symbol is never a prefix of the bit string representing any other symbol) that expresses the most common characters using shorter strings of bits than are used for less common source symbols.
Example: 7 / 3 / 1 / (-1) / 4 / 0 ® 01111 / 011 / 1/ 101 / 00100 / 0
Variable Length Code (VLC): In coding theory a variable-length code is a code which maps source symbols to a variable number of bits.
Run Left Encoding (RLE): RLE is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run.
Example: Input data – 22222222288881111111 Code – 2,9 8,4 1,7
Figure 10. DCT, quantization, zigzag scanning
Printing Graphic Design
Printing is to send the digital data to the printer or plotter and to see them as a picture in a paper. To see the graphic design in a paper as same as its original copy, it must be chosen the right-sized paper for supporting the resolution value.
For example if the resolution is 2048 ´ 1536 pixcel, Picture has got 2048 pixcels horizontally and 1536 pixcels vertically. In a real colour printing 1 inch consists of 300 pixcels. So;
A graphic design in 2048 ´ 1536 resolution can be printed 17 ´ 15 cm paper sized in real colour mode.
CONCLUSION and SUGGESTION
To implement graphics with computers, computers strong in hardware and software are needed. The mainboard, CPU, RAM, graphics card and hard disc hardware of the computer should be capable of preparing graphics. The main board of the graphics designing computer should have the data bus which will realize a fast communication between the main board and the CPU, RAM and hard disc. The main board data bus speed should be minimum 800 MHz. The CPU should have HT or Dual Core Technologies and the internal cache memory capacity should be 2 MB. Graphics files have big memories. System memory should be big enough to hold the graphics files which are needed to run at the same time in its memory. The minimum system memory should be 1 GB. The graphics design computer should have the graphics processor which can make the graphics card image calculations and 2d/3D image operations, an video memory which can take a high resolution image quality, and the specification of converting the digital signals to analog signals in high screen refresh rate. The hard disc should have the minimum capacity of 80 GB since it would store large graphics files.
Vector based and pixcel based application softwares are used when developing graphics applications. The largest different between vector and pixcel graphic is; the picture is made up of pixcels in pixcel based graphics. When the picture zoomed in the pixcels becaome obvious and the Picture is spoiled. On the other hand, in vectoral graphics the Picture doesn’t disturb and the pixcels aren’t seen.
The resolution values should be specified according to the size of the graphic to be prepared. The graphics card of the computer specifies the system’s resolution ability. The lowest resolution graphic cards are 640´480 pixcel VG and the highest resolution graphic cards are 2560´2048 QSXGA.
Different file types which were produced with desktop publishing graphics application software, same common image formatsa re produced to make them run with different application software. The most common formatsa re pict, eps, png, gif, jpeg, bmp and psd. Jpeg converts the large graphic files into small files by compressing them.
The printing size of the graphic according to the screen area should be specified to protect the quality when printing thr graphic files. For this end, the graphics should be designed with the output size in mind.
To get high performance, the software and hardware should be right configurated.
REFERENCES
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6. ÖZGÜLER, M. (2005) Bilgisayar Donanımı. Abp Press, Trabzon
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8. FRASER, B. and others. (2005). Real World Color Management. Peachpit Press. USA.
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12. BRITTAIN, D.L. (1990). Portability of Interactive Graphics Software. IEEE Computer Graphics & Applications.
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