Re: Creating a color image with NSBitmapImageRep and greyscale data
Re: Creating a color image with NSBitmapImageRep and greyscale data
- Subject: Re: Creating a color image with NSBitmapImageRep and greyscale data
- From: Jason Horn <email@hidden>
- Date: Tue, 27 Nov 2007 23:37:08 -0500
Dave,
Actually, there was a bug in my code. That loop should have been:
for (pixel=0; pixel<numPixels; pixel++) {
RGBData[RGBpixel] = pixels[pixel];
RGBData[RGBpixel+1] = pixels[pixel];
RGBData[RGBpixel+2] = pixels[pixel];
RGBpixel += 3;
}
So, now I have a color image (that is grey), but CIColorMap still does
not produce a color image. Perhaps I don't understand how CIColorMap
works.
On Nov 27, 2007, at 10:55 PM, David Spooner wrote:
Sorry, I meant to also say that an alternative to this quick and
dirty approach is to consider the input greyscale value as the hue
component of an HSB (or related) colorspace and perform a standard
conversion from HSB to RGB (using a fixed saturation and brightness).
dave
On 27-Nov-07, at 8:34 PM, David Spooner wrote:
The preceding line sets the r, g and b components uniformly for
each output pixel, so you'll always get grey. You might try
distributing each input pixel p across r, g and b along the lines
of...
int bpr = [bitmap bytesPerRow];
for (int i = 0; i < height; ++i) {
char *row = bitmapData + i * bpr;
for (int j = 0; j < width; ++j) {
uint16_t p = pixels[i * width + j];
unsigned char *rgb = row + j * 3;
rgb[0] = p & 0x3f;
rgb[1] = (p >> 6) & 0x3f;
rgb[2] = (p >> 12);
}
}
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