- There are two types of image compression; lossless and lossy.
- A lossless compression compresses image data without discarding any of the data. Therefore, when the image is decompressed, there is no evidence that the image was ever compressed.
- A lossy compression scheme discards some of the image data in order to achieve higher compression ratios.
- JPEG is a lossy compression, to save space it just throws away parts of an image.
- JPEG compression works best on images with continuous tone such as photographs and paintings.
- Images should have at least 16 levels of gray to considered for JPEG compression.
- JPEG compression is quickly becoming a standard for image transfer on the Internet.
- Another type of compression that goes with Jpeg is Huffman.
- This is used as a compression method in imaging and video as well as in other areas. The idea behind Huffman coding is simply to use shorter bit patterns for more common characters, and longer bit patterns for less common characters.
- As the pictures show below how the quality of the pictures change as you compress it.
- The first picture has been compressed by 20%, while the other one by 90%.
GIF Compression
- This is a lossless method of compression.
- All that means is that when the program that creates a GIF, it squashes the original image down taking care not to lose any data.
- The picture below shows how when you change the look of a gif, how the size changes as well.
The far left picture is the original one which is 6.7k, the middle one has been flipped and is now 11.5k and the far right one has noise added to it and is now 56k.
- For further information click the links below