I have a lot of .png images, and I want to replace a color to another color..
Is there a batch program to do that? I'm on Windows 7
I think the same answer I gave you here can be applied to this question as well.
It depends on what graphical programs you have, but Photoshop Elements is fairly cheap and you can batch process.
The issue is it really depends on how complex your .png images are - for example, if your images are just black and white then this should be be quite an easy task with accurate results - however, if your image is a picture with various hues and shades of colours this task becomes more complicated and batch processing may not be possible. For example, you want to replace green with red. Well, what shade of green? Some green's have yellow in and where some may describe a colour as 'yellowy green' others may describe it as a 'greeny yellow'... This obviously makes direct colour chnage over a range of colours more difficult to define. Therefore, it may even require part batch and part manual.
This is of course assuming you know how to use these type of programs.
For a single color replacement I suggest you use XnView's batch processing tool:
If you need to replace a range of colors, or use tolerance settings (especially useful for JPEG images where neighboring pixels might have slightly different colors - sometimes imperceptible to the eye), I recommend Batch Images. It's also more user friendly for batch processing:
Disclaimer: I am a frequent user of both XnView and Batch Images.