Color Quantizer is described as 'Color quantizer is a small program allows you to easily optimize images for web' and is an app in the Photos & Graphics category. There are three alternatives to Color Quantizer for a variety of platforms, including Mac, Windows, XnView, Adobe Photoshop and GIMP. The best alternative is RIOT - Radical Image Optimization Tool, which is free. Other great apps like Color Quantizer are ImageAlpha (Free, Open Source) and Ximagic Quantizer (Paid).
Saving images for web/email/other media with the best compression ratio and quality is a difficult task if you don’t have the right tools. Choosing the right format then choosing the right parameters are the key factors of smaller files.
ImageAlpha is a GUI for pngnq and pngquant. It allows you to easily generate paletted PNG images with full alpha channel. These images are usually 40-60% smaller than 24-bit PNG, and still can have semitransparent colors.