2b Bitmapped Graphics Storage
- 1. Bit-Mapped Graphic Data: Storage of Graphic Data - Technical Terms Multimedia - Section 2
- 2. Bit-mapped Graphic Data To calculate the approx file size of an uncompressed bitmap: Files size (bytes) = Number of Pixels x colour depth per pixel (bits) 8 If colour depth per pixel is in bytes : Files size = Number of Pixels x colour depth per pixel
- 3. Bit-mapped Graphic Data Dithering Extra colour can be created by placing different colours next to each other Red and blue pixels would appear as purple
- 4. Dithering Example 256 Colour 4 Colour Non-Dithered 4 Colour with Dithering
- 6. Bit-mapped Graphic Data Anti alias Low resolution images can appear less jaggy if extra colours are used to reduce staircase effect
- 7. Bit-mapped Graphic Data Re-sampling If detail is lost in a graphic it is not possible to retrieve it Re-sampling will make a best guess at what the missing pixels would look like Technique used to enhance grainy security camera images
- 8. Trading quality for file size Resolution: increasing resolution increases the number of pixels, can improve the quality of a graphic but increases the file size. Colour depth : increasing colour depth increases the number of colours or shades of grey, can improve the quality of a graphic but increases the file size. Lossy compression: reduces file size and, providing the rate of compression is not too high, does not affect the quality of the graphic.
- 9. Bit-Mapped Graphic Data: Output of Graphic Data Multimedia - Section 2
- 10. Graphics cards The graphics card is the device in the computer responsible for generating images. Images are held in the memory of the graphics card (called VRAM - or Video RAM).
- 11. Digital to Analogue Converter (DAC) Converts the digital computer signal into an analogue one that the monitor needs. In future analogue displays will be replaced with ones that accept digital signals Many LCD displays currently allow digital signals Called DVI - Digital Visual Interface Digital Image Signal DAC on Graphics Card Analogue Image Signal
- 12. Graphics Processing Unit (GPU) The GPU is a Digital Signal Processor (DSP) Located on the graphics card Often more advanced than CPU Created mainly for modern gaming Generates images faster and with better quality than if generated from the processor
- 13. Hardware for Displaying 2D Graphics CRT monitor: Bulky & heavy Run on mains power Cost less than equivalent TFT screens LCD and TFT screens: Flat & light Need less power More expensive than CRT