Method: Magick::Image#add_compose_mask

Defined in:
ext/RMagick/rmimage.cpp

#add_compose_mask(mask) ⇒ Object

Associates a mask with an image that will be used as the destination image in a #composite operation.

The areas of the destination image that are masked by white pixels will be modified by the #composite method, while areas masked by black pixels are unchanged.

Parameters:

See Also:



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# File 'ext/RMagick/rmimage.cpp', line 647

VALUE
Image_add_compose_mask(VALUE self, VALUE mask)
{
    Image *image, *mask_image = NULL;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
    Image *clip_mask = NULL;
#endif

    image = rm_check_frozen(self);
    mask_image = rm_check_destroyed(rm_cur_image(mask));
    if (image->columns != mask_image->columns || image->rows != mask_image->rows)
    {
        rb_raise(rb_eArgError, "mask must be the same size as image");
    }

#if defined(IMAGEMAGICK_7)
    clip_mask = rm_clone_image(mask_image);

    exception = AcquireExceptionInfo();
    GVL_STRUCT_TYPE(NegateImage) args_NegateImage = { clip_mask, MagickFalse, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(NegateImage), &args_NegateImage);
    rm_check_exception(exception, clip_mask, DestroyOnError);
    GVL_STRUCT_TYPE(SetImageMask) args_SetImageMask = { image, CompositePixelMask, clip_mask, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(SetImageMask), &args_SetImageMask);
    DestroyImage(clip_mask);
    CHECK_EXCEPTION();
    DestroyExceptionInfo(exception);
#else
    // Delete any previously-existing mask image.
    // Store a clone of the new mask image.
    GVL_STRUCT_TYPE(SetImageMask) args_SetImageMask = { image, mask_image };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(SetImageMask), &args_SetImageMask);
    GVL_STRUCT_TYPE(NegateImage) args_NegateImage = { image->mask, MagickFalse };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(NegateImage), &args_NegateImage);

    // Since both Set and GetImageMask clone the mask image I don't see any
    // way to negate the mask without referencing it directly. Sigh.
#endif

    return self;
}