Method: Magick::Image#random_threshold_channel

Defined in:

ext/RMagick/rmimage.cpp

#random_threshold_channel(geometry_str, channel = Magick::AllChannels) ⇒ Magick::Image #random_threshold_channel(geometry_str, *channels) ⇒ Magick::Image

Changes the value of individual pixels based on the intensity of each pixel compared to a random threshold. The result is a low-contrast, two color image.

Overloads:

• #random_threshold_channel(geometry_str, channel = Magick::AllChannels) ⇒ Magick::Image

  Parameters:

  • geometry_str (Magick::Geometry, String) —

    A geometry string containing LOWxHIGH thresholds.

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

    a ChannelType arguments.

• #random_threshold_channel(geometry_str, *channels) ⇒ Magick::Image

  Parameters:

  • geometry_str (Magick::Geometry, String) —

    A geometry string containing LOWxHIGH thresholds.

  • *channels (Magick::ChannelType) —

    one or more ChannelType arguments.

Returns:

• (Magick::Image) —

  a new image

See Also:

• https://www.imagemagick.org/Magick++/Geometry.html

# File 'ext/RMagick/rmimage.cpp', line 11366

VALUE
Image_random_threshold_channel(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    ChannelType channels;
    char *thresholds;
    VALUE geom_str;
    ExceptionInfo *exception;

    image = rm_check_destroyed(self);

    channels = extract_channels(&argc, argv);

    // There must be 1 remaining argument.
    if (argc == 0)
    {
        rb_raise(rb_eArgError, "missing threshold argument");
    }
    else if (argc > 1)
    {
        raise_ChannelType_error(argv[argc-1]);
    }

    // Accept any argument that has a to_s method.
    geom_str = rb_String(argv[0]);
    thresholds = StringValueCStr(geom_str);

    new_image = rm_clone_image(image);

    exception = AcquireExceptionInfo();

#if defined(IMAGEMAGICK_7)
    BEGIN_CHANNEL_MASK(new_image, channels);
    {
        GeometryInfo geometry_info;

        ParseGeometry(thresholds, &geometry_info);
        GVL_STRUCT_TYPE(RandomThresholdImage) args = { new_image, geometry_info.rho, geometry_info.sigma, exception };
        CALL_FUNC_WITHOUT_GVL(GVL_FUNC(RandomThresholdImage), &args);
    }
    END_CHANNEL_MASK(new_image);
#else
    GVL_STRUCT_TYPE(RandomThresholdImageChannel) args = { new_image, channels, thresholds, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(RandomThresholdImageChannel), &args);
#endif
    rm_check_exception(exception, new_image, DestroyOnError);

    DestroyExceptionInfo(exception);

    RB_GC_GUARD(geom_str);

    return rm_image_new(new_image);
}