[Image-SIG] Colorize Image

[Laura & Edward Cannon]

There is a function for this. from the handbook:
ImageOps.colorize(image, black, white) => image

Colorize grayscale image. The black and white arguments should be RGB
tuples or color names; this function calculates a colour wedge mapping
all black pixels in the source image to the first colour, and all
white pixels to the second colour.

call it with your color for black and white for white, it accepts all
"standard" color specifications, such as "#ff2253" or (255, 0, 0).

On Thu, Feb 11, 2010 at 3:50 AM,  <jcupitt at gmail.com> wrote:
> On 10 February 2010 11:01, Espen Moe-Nilssen <espen at medialog.no> wrote:
>> We are making an open source project, http://plone.org/products/subskins
>> I have been trying over and over again to find a way to let PIL colorize an
>> image.
>> It should work like this:
>> 1) I have a greyscale image
>> 2) A color is selected, for example "#123456"
>> 3) The image is colorized in this way:
>>     Whatever was white is still white
>>     Whatever was black (100%) is now "#123456"
>>     Whaterver was grey (50%) is now 50% of "#123456"
>> I have tried a lot of different approaches, but the colors always come out
>> too dark. Is there a way to do this ?
>
> You need to split the image into luminance (your greyscale image) and
> colour (the constant colour you want to apply).
>
> If you imagine the RGB space as a cube, the neutral axis (all the grey
> colours) is a straight line from (0, 0, 0) to (255, 255, 255). What
> you want to do is translate that line (ie. keep the angle of the thing
> the same, just translate the whole line up/down/left/right/fwd/back)
> so that it passes through #123456 instead. Any bits that go over 255
> or under 0 need to be clipped.
>
> This is easy in CIELAB space, but still OK in RGB.
>
> John
> _______________________________________________
> Image-SIG maillist  -  Image-SIG at python.org
> http://mail.python.org/mailman/listinfo/image-sig
>