Color Conversion

here it is a color conversion method i use.

hoping this will help.

int
ColorConverter::ConvertColor(AIColor* srcCol, AIColorConversionSpaceValue dstSpace, AIColor *dstCol, AIReal srcAlpha, AIReal *dstAlpha)
{
    // determine srcCol's space and sample size:
    AIColorConversionSpaceValue srcSpace;
    int srcSize;
    bool srcHasAlpha = srcAlpha < 1;
    switch (srcCol->kind) {
        case kGrayColor:
            srcSize = 1;
            if (srcHasAlpha) srcSpace = kAIAGrayColorSpace;
            else srcSpace = kAIGrayColorSpace;
            break;
        case kThreeColor:
            srcSize = 3;
            if (srcHasAlpha) srcSpace = kAIARGBColorSpace;
            else srcSpace = kAIRGBColorSpace;
            break;
        case kFourColor:
            srcSize = 4;
            if (srcHasAlpha) srcSpace = kAIACMYKColorSpace;
            else srcSpace = kAICMYKColorSpace;
            break;
        default:
            return -1;
    }

    bool dstHasAlpha = dstSpace == kAIACMYKColorSpace || dstSpace == kAIARGBColorSpace || dstSpace == kAIAGrayColorSpace;

    if (srcSpace >= 0 && dstSpace >= 0) {
        AISampleComponent src[5];
        AISampleComponent dst[5];
        memcpy(src, &srcCol->c, srcSize * sizeof(AISampleComponent));
        if (srcHasAlpha) src[srcSize] = srcAlpha;
        // TODO: why swapping kGrayColor???
        if (srcCol->kind == kGrayColor) src[0] = 1.0f - src[0];
        ASBoolean inGamut;

        AIColorConvertOptions options;
        sAIColorConversion->ConvertSampleColor(srcSpace, src, dstSpace, dst, options, &inGamut);

        if (dstCol == NULL)
            dstCol = new AIColor;
        // init the destCol with 0
        // memset(dstCol, 0, sizeof(AIColor));
        // determine dstCol's kind and sampleSize:
        int dstSize;
        switch (dstSpace) {
            case kAIMonoColorSpace:
            case kAIGrayColorSpace:
            case kAIAGrayColorSpace:
                dstCol->kind = kGrayColor;
                dstSize = 1;
                break;
            case kAIRGBColorSpace:
            case kAIARGBColorSpace:
                dstCol->kind = kThreeColor;
                dstSize = 3;
                break;
            case kAICMYKColorSpace:
            case kAIACMYKColorSpace:
                dstCol->kind = kFourColor;
                dstSize = 4;
                break;
            default:
                return NULL;
        }
        // TODO: why swapping kGrayColor???
        if (dstCol->kind == kGrayColor) dst[0] = 1.0f - dst[0];
        memcpy(&dstCol->c, dst, dstSize * sizeof(AISampleComponent));
        // get back alpha:
        if (dstAlpha != NULL)
            *dstAlpha = dstHasAlpha ? dst[dstSize] : 1;
       
        return 0;
    }
    return -1;
}

best regards,

Thomas.

You can definitely convert form RGB or CYMK (or a couple of others I don't actually know how to use) into gray scale. You basically just call AIColorConversionSuite::ConvertSampleColor() and give it the to & from colour spaces along with a couple of arrays representing the source colour & a buffer in which to stick the result. There are some options (AIColorConvertOptions) and a gamut boolean, but its fairly straightforward.