pbmplus

How to set threshold when converting JPEG to non-dithered bitmap?

I'm using my digital camera as a quick and dirty scanner. Resolution is actually around 300dpi, which is quite reasonable. But my camera produces a color image, which I want reduced to a bitmap. I do not want to dither the image; I'm looking for what I would get if I put the document through a black-and-white scanner. Converting a JP...

How to scale pixels in an image to adjust brightness?

I have a grayscale image from a photograph. I've determined that certain parts of the image are underilluminated, and that a pixel with luminance Y = 0.8 should actually be adjusted to 90% grey, i.e., that pixel should be given luminance 0.9. My question is how do I scale the other pixels nearby? I'm pretty sure multiplying all the lu...