The following research was conducted on the BMP file below the program used was paintshop pro and it was simply the saving of the same image in different formats.
The original BMP image is in a rasterised format in which the image was uncompressed and lossless the image pixels were very smooth with no loss in colour depth. Below are the results of each compression
JPEG
- Compression level 1- There is very little difference between the BMP and JPEG at a compression level of 1. Pixel positioning and colour depth remains quite similar and at the size of the image no quality is lost. The file size takes a huge leap down from the original 6.2Mb to the now new 538Kb shedding down the file size 92%.
- Compression Level 10- The same applies to the compression level of 10 there is no major differences apart from a few pixels being merged where as in the BMP they were seperate colours however the size has also reduced 66% from the level 1 compresion file format. An average of 4% per compression level is assumed for file size reduction. The file size at level 10 is 235kb.
- Compression Level 20- In compression level 20, the gradual loss of colour is seen as pixels are not as smoothly alligned as in the BMP little loss of colour is evident however the image still looks good from its original view. File size has now dramatically decreased bringing it down to 145Kb. A reduction of 98% from the original BMP file size.
- Compression Level 50- At a compression level of 50 the images quality is dramatically reduced colour loss is evident and pixel positioning is not as accurate as in the uncompressed BMP single colours are merged and the pallete offered by the file is less then what is needed. The file size is reduced to 89.7kb
- Compression Level 75- There is not much difference between a level of 50 and 75 and all of the degrading properties remain exponential. the decay of colour loss is still evident, all propertys such as file size are still decreasing. The file size is now down to 65.3Kb
- Compression Level 99- At a compression level of 99 there is no need to even use the image as it is at such a low quality allowing the image to be at a very small size the pallete and pixel accuracy offered at this compression rate may be suitable for a very old computer however technology would not be that expensive to view an image at its Bitmap stage let alone at a compression level of 99. The file size at a level of 99 is 38.5kb
Below is a table which shows the file size percentages for each compression method with percentages.
TIFF
- Uncompressed- The TIFF uncompressed is at a file size of 6.59 Mb with no quality lost.
- Fax Method- The method has been created to allow images to be faxed in a two colour schema it is practical for two colour images however for the image that was being tested with the process created a mostly dark imnage with some white pixels, the file size was 86Kb.
- LZW- The LZW method compressed the file down to 1.79Mb giving it a very close to original quality with some colour loss.
Packbit- The packbit method also hardly compresses the file some colour quality is lost however the file remains at a quite large file size of 3.9Mb.
GIF
Apart from some quality loss the gif method is quite a practically format, the file size is cut down to 735kb from the original 6.2Mb pixels are also converted to single colours in some instances.
PNG
The PNG method would only be conventional if there is transparency available however the file is fairly compressed as it is 1.59 Mb.
