I have just used EE's native image manipulations for the first time and boy did they work great. However, my client looked at the site after I replaced the old images with the resized ones and her nice white backgrounds on products no longer looked white. It's very subtle, I have to look at my monitor at an angle to see it, but apparently it is quite noticeable on certain monitors. When I color sample these white backgrounds, I get an occasional #fefefe pixel. So on some monitors, it is giving the whole image background a yellow cast. I'm wondering if anyone has advice about increasing the quality of the image manipulations, or other ways of managing this particular problem. I see that I can specify a different library, but it's unclear to me if that would help. The images are jpg and I imagine that increasing the quality of the jpg might help, but I don't see settings for that.
By default I think EE sets the quality of the image at 90
You could try editing system/codeigniter/system/libraries/image_lib.php LINE 36 and change the
var $quality to 100
Other than that if you are using GD2 Image Resizing Protocol, try switching it to ImageMagick (if on your server) which may give a slightly better result.
I've seen odd things happen with images when the color profile is set to something other than sRGB. Check to make sure the color profile is using sRBG and not something like Adobe RBG or ProPhoto RBG. If you're using any type of Save for Web feature it will usually set the color profile to sRGB automatically.