Check if lossless WebP output is smaller at lossless quality

[yogendrasinh]

WebP lossless conversion sometimes leads to smaller images compared to lossy quality. This is especially possible with images that has less colors, large flat areas. Simple logos and some screenshots fall into this category. Input images are almost always PNG in such cases.

Gain

• Smaller Output: ~25% smaller file than images compressed at 80% for some image. Gain may vary for each image.
• Higher Quality: Lossless quality.

Trade off

• Increased Compression Time: Simplest approach is to compress images with lossy and lossless compression, both, to select lossless image as output image if size is smaller than lossy image.

Approach

• If input is PNG and output is WebP, then only check if lossless output is smaller.
• No user option to override this settings. Mass Image Compressor is designed to take the image compression headache away and not confuse user with options which most users do not understand.