Consider a application handling uploading of potentially very large PNG files.
All uploaded files must be stored to disk for later retrieval. However, the PNG files can be up to 30 MB in size, but disk storage limitations gives a maximum per file size of 1 MB.
The problem is to take an input PNG of file size up to 30 MB and produce an output PNG of file size below 1 MB.
This operation will obviously be lossy - and reduction in image quality, colors, etc is not a problem. However, one thing that must not be changed is the image dimension. Hence, an input file of dimension 800x600 must produce an output file of dimension 800x600.
The above requirements outlined above are strict and cannot be changed.
Using ImageMagick (or some other open source tool) how would you go about reducing the file size of input PNG-files of size ~30 MB to a maximum of 1 MB per file, without chaning image dimensions?