Legacy ImageMagick Discussions Archive

Hi all.

(Before replying check P.P.S)

Here's a bit more detail to what I'm trying to accomplish. I have a png image that has graphics and text. All relevant text is black and that's all that interestes me so I want to remove everything else. So I do this: It sort of works. The only problem is that afeter that when I try to convert the resulting png to tif the tif is somehow "corrupted". IM Display does show the image just fine, but I can't open it in paint nor in the standard windows image viewer, so there must be something funny going on. When I use the identify tool I see that the image changes from 8-bit DirectClass png -> 8-bit PseudoClass png -> 8-bit Grayscale DirectClass tif
Perhaps that's the problem, but I have no idea how to force IM to output the black & white picture as if it was colored.

P.S. Almost the same thing happens if I do things in the opposite order, firts convert to tiff and then remove all but black. The only difference is that it the picture changes from:
8-bit DirectClass png -> 8-bit DirectClass tif -> 1-bit Bilevel DirectClass tif

P.P.S LOL. 2 seconds afeter posting this I came up with yet another thing to try and it worked. I reverserd the order (which was probly irrelevant) and added the trigger -type TrueColor and now it produces nicely working tiffs. I thoght I had tried that already, but perhaps I misspelled TrueColor or had the trigger in wrong place... sry for the ponitless post

All colors but pure black to white.... -threshold 0
See
http://www.imagemagick.org/Usage/quantize/#threshold

OR -fill white +opaque black
The '+' form of opaque means NOT this color

That last can also use a -fuzz factor to say color not 'this close' to black.

See http://www.imagemagick.org/Usage/color/#opaque
and http://www.imagemagick.org/Usage/color/#fuzz

Thanks for the threshold tip. It seems to be quicker than that other method. Can I use it if I want to extract some other color than pure black? Let me specify that question a bit more. Lets say I have a picture that has 3 colors: white, black, green. Now would it be possible to use threshold to convert everything green in to black and everything else to white (including the old black areas)?

Alcareru wrote:Thanks for the threshold tip. It seems to be quicker than that other method. Can I use it if I want to extract some other color than pure black? Let me specify that question a bit more. Lets say I have a picture that has 3 colors: white, black, green. Now would it be possible to use threshold to convert everything green in to black and everything else to white (including the old black areas)?

convert inputimage -fill white +opaque green -fill black -opaque green resultimage

fmw42 wrote:

Alcareru wrote:Thanks for the threshold tip. It seems to be quicker than that other method. Can I use it if I want to extract some other color than pure black? Let me specify that question a bit more. Lets say I have a picture that has 3 colors: white, black, green. Now would it be possible to use threshold to convert everything green in to black and everything else to white (including the old black areas)?

convert inputimage -fill white +opaque green -fill black -opaque green resultimage

Thanks. I'm starting to get a hang of this Next I have a bit more comclicated question. I'll make new post out of it, though it remotely has something to do with this, but the original topic: "convert png all but black to white, convert to tif" wouldn't really describe it.