Method: Magick::Image#transparent_chroma

Defined in:
ext/RMagick/rmimage.cpp

#transparent_chroma(low, high, invert, alpha: Magick::TransparentAlpha) ⇒ Magick::Image

Changes the opacity value associated with any pixel between low and high to the value defined by opacity.

As there is one fuzz value for the all the channels, the transparent method is not suitable for the operations like chroma, where the tolerance for similarity of two color components (RGB) can be different, Thus we define this method take two target pixels (one low and one high) and all the pixels of an image which are lying between these two pixels are made transparent.

Returns a new image.

Parameters:

  • low (Magick::Pixel, String) —

    The low ends of the pixel range

  • high (Magick::Pixel, String) —

    The high ends of the pixel range

  • invert (Boolean) —

    If true, all pixels outside the range are set to opacity.

  • alpha (Numeric) (defaults to: Magick::TransparentAlpha) —

    The desired alpha.

Returns:



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# File 'ext/RMagick/rmimage.cpp', line 14760

VALUE
Image_transparent_chroma(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    Quantum alpha = TransparentAlpha;
    MagickPixel low, high;
    MagickBooleanType invert = MagickFalse;
    MagickBooleanType okay;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
#endif

    image = rm_check_destroyed(self);

    switch (argc)
    {
        case 4:
            if (TYPE(argv[argc - 1]) == T_HASH)
            {
                invert = (MagickBooleanType)RTEST(argv[3]);
            }
            else
            {
                invert = (MagickBooleanType)RTEST(argv[2]);
            }
        case 3:
            alpha = get_named_alpha_value(argv[argc - 1]);
        case 2:
            Color_to_MagickPixel(image, &high, argv[1]);
            Color_to_MagickPixel(image, &low, argv[0]);
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 2, 3 or 4)", argc);
            break;
    }

    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    GVL_STRUCT_TYPE(TransparentPaintImageChroma) args = { new_image, &low, &high, alpha, invert, exception };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(TransparentPaintImageChroma), &args);
    okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    GVL_STRUCT_TYPE(TransparentPaintImageChroma) args = { new_image, &low, &high, (Quantum)(QuantumRange - alpha), invert };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(TransparentPaintImageChroma), &args);
    okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
    rm_check_image_exception(new_image, DestroyOnError);
#endif
    if (!okay)
    {
        // Force exception
        DestroyImage(new_image);
        rm_magick_error("TransparentPaintImageChroma failed with no explanation");
    }

    return rm_image_new(new_image);
}