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Step 1: Make a Quick Selection
In my picture, I want the blue car to be green, but not the carpet, or anything in the background, so I need to roughly select the car.
Click on the lasso tool. Drag a quick selection around the car. Tweak the selection a bit using
Great. Car selected.
Step 2: Adjust the Hue
Select the blue swatch in the Hue Saturation window that pops up, and drag the hue slider around. Pretty good. Click OK.
Let us take a look at our picture without the crawling ants. Hit
Now I noticed a slight line on the floor near the selection edge. This is because there is a little blue light hitting the floor.
We can fix that by feathering the selection before adjusting the hue.
Step 3: Feather the Selection
Now go to Selection>Feather and change the value to, say 10 pixels. Click OK.
Adjust the hue again and look at your final picture. No line near the floor. Great.
Save your new picture.
Step 4: A Final Note
So the steps again are:
2)Feather the selection.
3)Adjust the Hue.