Re: Changing the background of a 1 bit bitmap?

FROM : R. Scott Thompson
DATE : Mon Oct 04 20:27:01 2004

>> On Oct 4, 2004, at 11:25 AM, Glen Simmons wrote:
>>

>>> I'm creating an NSImage from some 1 bit bitmap data using the
>>> -[NSBitmapImageRep initWithBitmapDataPlanes:pixelsWide: ...] method
>>> passing NSCalibratedBlackColorSpace so that 1 bits become black
>>> pixels and 0 bits become white pixels. I'd like the 0 bits to become
>>> a color of my choice instead of white. Is there an easy way to do
>>> this?

>>
>> What you want is a different Compositing operation
>> (NSCompositeSourceOver I think).  There doesn't appear to be a way to
>> do that with an NSImageView.  Perhaps you could create a custom view
>> and use NSImage calls yourself?

>
> I did say "easy". :-)  I was thinking this could be done at the time
> of creation. The replacement color would always be the same, so I
> figured some particular value passed as the colorSpaceName: parameter
> would do it. Not so?


Nah... the color space name would just let you specify how you wanted
that background color to be specified (i.e. I want to specify the
background color as CMYK, or RGB, or RGB as intepreted by thus and such
a digital camera).  You might be able to do something wacky with
creating an indexed color space and convincing it to use that... but I
think you'd end up having to create a color profile on the fly and much
pain and suffing would ensue.  Before you got that far, you'd be better
off using NSQuickDrawView and just create a GWorld with a custom
palette.

How about using NSBitmapImageRep and
colorizeByMappingGray:toColor:blackMapping:whiteMapping:  It's really
long but might help.

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