Method: Magick::Image#channel_compare

Defined in:
ext/RMagick/rmimage.cpp

#compare_channel(image, metric, channel = Magick::AllChannels) ⇒ Array #compare_channel(image, metric, channel = Magick::AllChannels) {|opt_args| ... } ⇒ Array #compare_channel(image, metric, *channels) ⇒ Array #compare_channel(image, metric, *channels) {|opt_args| ... } ⇒ Array

Compare one or more channels in two images and returns the specified distortion metric and a comparison image.

Overloads:

  • #compare_channel(image, metric, channel = Magick::AllChannels) ⇒ Array

    Parameters:

    • image (Magick::Image, Magick::ImageList) —

      Either an imagelist or an image. If an imagelist, uses the current image.

    • metric (Magick::MetricType) —

      The desired distortion metric.

    • channel (Magick::ChannelType) (defaults to: Magick::AllChannels) —

      a ChannelType arguments.

  • #compare_channel(image, metric, channel = Magick::AllChannels) {|opt_args| ... } ⇒ Array

    When a block is given, compare_channel yields with a block argument you can optionally use to set attributes.

    • options.highlight_color = color

      • Emphasize pixel differences with this color. The default is partially transparent red.

    • options.lowlight_color = color

      • Demphasize pixel differences with this color. The default is partially transparent white.

    Parameters:

    • image (Magick::Image, Magick::ImageList) —

      Either an imagelist or an image. If an imagelist, uses the current image.

    • metric (Magick::MetricType) —

      The desired distortion metric.

    • channel (Magick::ChannelType) (defaults to: Magick::AllChannels) —

      a ChannelType arguments.

    Yields:

    • (opt_args)

    Yield Parameters:

  • #compare_channel(image, metric, *channels) ⇒ Array

    Parameters:

    • image (Magick::Image, Magick::ImageList) —

      Either an imagelist or an image. If an imagelist, uses the current image.

    • metric (Magick::MetricType) —

      The desired distortion metric.

    • *channels (Magick::ChannelType) —

      one or more ChannelType arguments.

  • #compare_channel(image, metric, *channels) {|opt_args| ... } ⇒ Array

    When a block is given, compare_channel yields with a block argument you can optionally use to set attributes.

    • options.highlight_color = color

      • Emphasize pixel differences with this color. The default is partially transparent red.

    • options.lowlight_color = color

      • Demphasize pixel differences with this color. The default is partially transparent white.

    Parameters:

    • image (Magick::Image, Magick::ImageList) —

      Either an imagelist or an image. If an imagelist, uses the current image.

    • metric (Magick::MetricType) —

      The desired distortion metric.

    • *channels (Magick::ChannelType) —

      one or more ChannelType arguments.

    Yields:

    • (opt_args)

    Yield Parameters:

Returns:

  • (Array) —

    The first element is a difference image, the second is a the value of the computed distortion represented as a Float.



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# File 'ext/RMagick/rmimage.cpp', line 3439

VALUE
Image_compare_channel(int argc, VALUE *argv, VALUE self)
{
    Image *image, *r_image, *difference_image;
    double distortion;
    VALUE ary, ref;
    MetricType metric_type;
    ChannelType channels;
    ExceptionInfo *exception;

    image = rm_check_destroyed(self);

    channels = extract_channels(&argc, argv);

    if (argc > 2)
    {
        raise_ChannelType_error(argv[argc-1]);
    }
    if (argc != 2)
    {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 2 or more)", argc);
    }

    rm_get_optional_arguments(self);

    ref = rm_cur_image(argv[0]);
    r_image = rm_check_destroyed(ref);

    VALUE_TO_ENUM(argv[1], metric_type, MetricType);

    exception = AcquireExceptionInfo();
#if defined(IMAGEMAGICK_7)
    BEGIN_CHANNEL_MASK(image, channels);
    GVL_STRUCT_TYPE(CompareImages) args = { image, r_image, metric_type, &distortion, exception };
    difference_image = (Image *)CALL_FUNC_WITHOUT_GVL(GVL_FUNC(CompareImages), &args);
    END_CHANNEL_MASK(image);
#else
    GVL_STRUCT_TYPE(CompareImageChannels) args = { image, r_image, channels, metric_type, &distortion, exception };
    difference_image = (Image *)CALL_FUNC_WITHOUT_GVL(GVL_FUNC(CompareImageChannels), &args);
#endif
    rm_check_exception(exception, difference_image, DestroyOnError);
    DestroyExceptionInfo(exception);

    ary = rb_ary_new2(2);
    rb_ary_store(ary, 0, rm_image_new(difference_image));
    rb_ary_store(ary, 1, rb_float_new(distortion));

    RB_GC_GUARD(ary);
    RB_GC_GUARD(ref);

    return ary;
}