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Graphics compression
- There are mainly three types of graphic formats:
- Bitmap
- .bmp filenames
- for each pixel, the bitmap format records information
- it takes a large amount of Hard Disk space.
- Graphics Interchange Format
- .gif filenames
- used for pictures with large areas of same colour
- groups areas of same colour together
- Mpeg
- .jpg filenames
- use a high compression algorithim
- called jpeg
- used for photos because these have no groups of pixels next to each other which are the same.
Practice:
- Enter the paint program and save a blank picture in the document
- Note that the file size should be very small as the picture is blank. But, it is large.
- Draw in the picture and save it again, now check with the supposition that it should be a larger filename. But, it is still the same size.
- Now save the same picture as GIF and note the slight change of colour tones. Now see the file size and it should be relatively minute.
- Now save the picture as a JPG and this time note the large difference in colour tones and definition. Check the filesize.
- Open a photo quality bitmap and note that no pixel is the same as its adjacent.
- Save as GIF and note the poor quality it becomes, and small size on disk.
- Lastly, save it as a JPG and note the negligible difference it makes, note it’s smaller size on disk.
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