The fastest, easiest, and most 'neutral' way to fix an issue like this is with an eyedropper Levels adjustment (available in Photoshop and GIMP):
- use the Black point eyedropper and click an decal area that should be black, but is not
- use the White point eyedropper to click an area the should be white, but is not
The key is not to click an area that is already black or white. In the decal posted by the OP, the black is not bad, so you can click just about any black and get good results. Otherwise, find a dark gray area that should be black and click it with the black point eye dropper. For the white, you need to find the most 'discolored' white, which looks to the be the area between the two Centuri logos. You can click as many places as you need with the white point eye dropper until you get the best results. (There are better methods to use, but this is quick and easy.)
Basically you are 'clipping' the colors - anything darker than the black color you click on becomes black, and anything lighter than the light area you click on becomes white. In the vast majority of cases it will restore black and white without having a detrimental effect on colors.
The issue with Brightness and Contrast controls is that you generally can't have both - good blacks and good whites. If you look at the example using B/C, you can clearly see the whites still have a significant yellow tint near the Centuri logos
The other Three rules of Decal Club:
- if you have straight lines, you must scan the decal parallel to the scanner to avoid aliasing
- you must scan at 200 pixels/inch or better
- you must NEVER USE JPG! ONLY PNG or TIF!!
The decal posted by the OP does not have enough pixels to properly reproduce and there is clear aliasing in the lines of the small American flag, but at least it was saved as the PNG. The Goonydent decals were saved as JPG and show clear signs of JPG artifacts.
Tony
cleaned up with Levels eyedropper (Photoshop – literally, 2 clicks, one with each eyedropper):
aliasing caused by a tilted scan - you can see missing pixels caused by aliasing in the middle fo the flag (color exaggerated to show effect, but also clearly visible in post #2 above):
by straightening the image, aliasing is reduced
instead of a clean white background in PNG format, saving in JPG format adds random looking noise all around and inside each area of color:
Below is an inverted color difference of the flag portion of the decal saved as PNG and as JPG. The colors you see are the changes made to the original file by the JPG compression algorithm. It's clearly visible how many pixels are affected by JPG compression and are no longer their original color: (a pure white image means no pixels are affected, pure black means every pixel was completely changed)
disclosure: Adobe certified Photoshop Instructor/Expert, over 30 years of working with digital images
