Reducing Bit Depth and Optimizing PNGs for the Web
Retrobatch comes built in with a great PNG compressor. To reduce the bit depth of PNGs even more, download and install ImageAlpha.
Once ImageAlpha is installed, restart Retrobatch and the options under the "ImageAlpha" node will be available:
With these options, PNG image color palettes can be reduced from millions of colors down to 512, 256, or even lower. And after checking the 'dither' option it will be difficult to tell any difference between the original and the ImageAlpha version. Take the following example below.
Processed with Retrobatch + PNG Crush, 310KB
Processed with ImageAlpha, 121KB
There are two images, the one on the left is processed by Retrobatch + the built in PNG Crush, and the one on the right is processed by ImageAlpha. The ImageAlpha version has its colors reduced to 256 and the file is 2.5 times smaller! That's a huge space savings with no noticeable difference between the two images.
Grab ImageAlpha and run Retrobatch against your existing PNG images to see what it can do.