Re: Web Images and Color

So, your source is compressed web images, and your output is web compressed images? Are you editing the files?
PNG is a good web format, comparable even to TIFF with LZW compression in quality, which is lossless, but not for web.
However, PNG browser support varies between browsers, especially when transparency is a factor.
JPEGs saved at 100% are visually lossless. I like to save JPEGs at 80% quality to maintain a "high(er) quality" appearance.
Don't scale-up raster images, and use Bilinear Interpolation for down-scaling.
Image Doctor, for PhotoShop, has a decent JPEG repair filter. And, If your do need to upscale, consider Genuine Fractals.