How to compress images without losing quality
Solution 1:
The very powerful command line utility convert allows extremely high quality bulk image processing.
Your only option to compress images without loosing any quality is keeping the image intact, and compress it using lossless compression.
However, that may not be what you are after. You refer to a website, and a concern of quick loading. If you want to address that issue, you probably will need to accept loosing some quality. There is limited scope to reduce image file size without loosing quality.There is huge scope to reduce image file size for websites without loosing perceptial quality, i.e., without noticing the loss in quality compared to showing the original image on the same website.
If, unless what you ask, the above has persuaded you that you are prepared to "loose some quality" nevertheless, then
- Reduce the resolution of the image to match the resolution of a computer screen.
- Use lossy jpeg compression. Tune the compression to achieve maximum compression without introducing unacceptable quality loss.
Depending on the original resolution of your graphics, that may reduce the file size to a tiny fraction of the original, without anyone noticing on the website except for the immediate loading.
convert is perfectly suited for these tasks, and can be automated for bulk processing.