Re: [Gimp-developer] suggestion for color to alpha
Hi, Daniel Egger [EMAIL PROTECTED] writes: Am 06 Sep 2001 12:56:46 +0200 schrieb Sven Neumann: I think Branko is right here. Color-To-Alpha is not suited for chroma-keying since it will remove all shades of blue from all colors in the image. Classic blue-boxing requires to clear only exactly the color defined as the blue-box background. This can easily be achieved using Select-By-Color with a small threshold followed by Clear. I believe a good chroma keying algorithm would have to work a bit differently because in real life one has the problem that the blue of bluebox might vary slightly because of lighting conditions. So maybe the best would be to go over the HSV colorspace to allow a choosable variance in the keycolor? Select_By_Color takes care of that but operates only in the RGB domain. It might be a good idea to add an option that allows to apply the threshold to the HSV colorspace. If someone wants to hack this simple function, please port by_color_select to libgimpcolor and add generic color_distance functions to libgimpcolor. Salut, Sven ___ Gimp-developer mailing list [EMAIL PROTECTED] http://lists.xcf.berkeley.edu/mailman/listinfo/gimp-developer
Re: [Gimp-developer] suggestion for color to alpha
Sven Neumann [EMAIL PROTECTED] writes: Hi, Branko Collin [EMAIL PROTECTED] writes: Does image/Select/By Color what you want? I think Branko is right here. Color-To-Alpha is not suited for chroma-keying since it will remove all shades of blue from all colors in the image. Classic blue-boxing requires to clear only exactly the color defined as the blue-box background. This can easily be achieved using Select-By-Color with a small threshold followed by Clear. That works fine for opaque objects, but not for translucent ones. For example, when you have someone with long hair you can see some of the blue background through the hair, so the colour in those pixels is a mixture of the hair colour and and the blue background. Even with opaque objects you still have pixels along the edge of the object where you get blue mixed in. Using Select-by-Colour to remove the blue leaves a blue fringe around the object. Select-by-Colour, Grow, Feather, Clear works better, but you still have blue around the object that should not be there. Tim ___ Gimp-developer mailing list [EMAIL PROTECTED] http://lists.xcf.berkeley.edu/mailman/listinfo/gimp-developer
Re: [Gimp-developer] suggestion for color to alpha
Rebecca J. Walter [EMAIL PROTECTED] writes: it might be useful if the color to alpha filter could a) interact with That reminds me: I'd like to use the color to alpha filter for chroma-keying. That is, stand the subject in front of a blue screen and use color-to-alpha to remove all the blue. However, the filter removes too much blue -- the resulting colour is as saturated as possible, even if the original colour wasn't so saturated. I'm thinking that it would be handy if the color-to-alpha had a preview and slider that went from 0 to 1, where 0 = do nothing and 1 = current behaviour and 0.5 gives a result half way between that for 0 and 1. Does this seem useful? Is there a better way to do this? just a thought. no, i can't prrogram it myself. I can program my idea if folks are interested. Tim ___ Gimp-developer mailing list [EMAIL PROTECTED] http://lists.xcf.berkeley.edu/mailman/listinfo/gimp-developer
[Gimp-developer] suggestion for color to alpha
it might be useful if the color to alpha filter could a) interact with the color picker or b) pull the information about the image background from the color tool stuff and use that as the color to replace. it isnt easy for a lot of users to select the color in the color selector without being able to pull that from the image. i just told a user how to use color picker to get the color code and enter that in the selector. it works, but it would be nicer if this tool were more user-friendly. just a thought. no, i can't prrogram it myself. and no, i will not whine about this repeatedly. just trying once to be helpful. :-) ___ Gimp-developer mailing list [EMAIL PROTECTED] http://lists.xcf.berkeley.edu/mailman/listinfo/gimp-developer
Re: [Gimp-developer] suggestion for color to alpha
Hi, Lourens Veen [EMAIL PROTECTED] writes: Open image Select Filters-color-to-alpha, popup appears Select color picker, another popup appears Get colour from image, it shows up in the color picker popup Drag the colour to the color-to-alpha popup Select OK You can also drag'n'drop colours from palettes and the Gimp main window. and additionally you can right-click the color-area to get a small menu that allows to take the global FB or BG color. Salut, Sven ___ Gimp-developer mailing list [EMAIL PROTECTED] http://lists.xcf.berkeley.edu/mailman/listinfo/gimp-developer
