How can I, most effortlessly, whiten or white out yellow or brown Tint?

Question

Is Tint the correct term?

These photos aren't mine. I can't retake them. Don't change anything except the yellowish Tint. In the first photo, the food pictures must NOT be DEsaturated or DEcolorized!

I'm referring any document, paper, or picture that appears too yellowish or brownish. I'm not merely referring Foxing. I prefer black text on white background. What's the most effortless way to remove the brownish Tint, or convert it to white? I prefer to use Irfanview as it loads up faster than GIMP. But apprise me if I must use GIMP for this purpose.

Answer 1

Two different problems. For photos of paper documents, it's mostly a problem of "color temperature" (your first image is a typical example), so with Gimp:

• Open the Sample points dialog (Windows > Dockable dialogs >Sample points)
• Create a sample point on an area that should be a neutral color (like the paper): Ctrl-drag from one of the rulers. The pixel's values should appear in the dialog, with a Red component bigger than the other two.
• Start Color > Color temperature and decrease the Intended temperature until you have approximately the same value for Red and Blue on the sample point.

The other image has a yellow background because the author wanted it so, it is not a general color shift. You wan make it grey use Levels on each channel and make the peaks of each channel (that represent the background pixels) occur roughly on the same values, but this will have unwanted effects elsewhere.

Answer 2

Depending on whether you're happy with a completely de-saturated image or not…

1. Just de-saturate the entire image. There are many ways to do this, from converting to greyscale, using hue/saturation or vibrance sliders etc

2. If you want to desaturate selected areas, use a mask

You can then use levels to emphasise the contrast - even right to black & white on some images.
These are very rough examples, just for demo purposes. You could do a whole lot better from the originals.

This is likely dependent, also, on what the original document was. From your posted images, 1, 3 & 4 are very likely not white to start with. Image 2 might be, but it's hard to tell.
Merely changing white balance will not be so effective if there isn't any true white in the image.