Legacy ImageMagick Discussions Archive

It is not surprised that the min is 0
because the pixel at x=42 to x=60 in dst.pgm is value 0.

The problem is the pixel at x=0 to x=41 is not value 0.

I see. I try to explain the problem again using the 256 pixel image. I made a single line gradation image, src.pgm, from black to white (using Ruby). The pixel value is 0 to 255. The value of leftmost pixel is 0. I convert it using ImageMagick: convert -level 20%,100%,0.5 src.pgm dst.pgm I checked ...

I agree that several black pixels are exist in dst.pgm. But that is not correspond to the black pixel in src.pgm. I simplified the test to a single pixel black image. The result image contains a pixel which color is grey11. % ruby -e 'STDOUT.binmode; print "P5\n1 1\n255\n\0"' > src.pgm % convert ...

I found "convert -level 20%,100%,0.5" doesn't preserve black. I made a simple PGM file which is gradation from black to white (using Ruby). The leftest pixel is black (value 0) and the rightest pixel (value 255) is white. "convert -level 20%,100%,0.5" converts the black pixel to a dark gray (value ...