PNG is a compressed format, but it changes less over the long haul than any of the others (when talking color). GIF changes a lot (and occasionally adds unwanted textures) over a lot of edits and resaves, but both will drift. Just edits and resaves will cause PNG colors to subtly drift, which is not good if you write and do your own illustrations as I do. The problem is exasperated if you feed it through a web site such as this one. The problem is bad enough I keep pictures who integrity is important in ZIP format when storing it at this site.
For B&W I use GIF as the standard, and for color images PNG is my standard. JPG has the highest compression ratio, and it always fuzzes the image (not good). Try taking a look at B&W images saved in that format, color hides a lot of sins. Only BMP is guaranteed not to change a picture, but with no compression it isn't popular.
For B&W I use GIF as the standard, and for color images PNG is my standard. JPG has the highest compression ratio, and it always fuzzes the image (not good). Try taking a look at B&W images saved in that format, color hides a lot of sins. Only BMP is guaranteed not to change a picture, but with no compression it isn't popular.