Method: Magick::Image#bilevel_channel

Defined in:
ext/RMagick/rmimage.cpp

#bilevel_channel(threshold, channel = Magick::AllChannels) ⇒ Magick::Image #bilevel_channel(threshold, *channels) ⇒ Magick::Image

Changes the value of individual pixels based on the intensity of each pixel channel. The result is a high-contrast image.

Overloads:

  • #bilevel_channel(threshold, channel = Magick::AllChannels) ⇒ Magick::Image

    Parameters:

    • threshold (Numeric) —

      The threshold value, a number between 0 and QuantumRange.

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

      a ChannelType arguments.

  • #bilevel_channel(threshold, *channels) ⇒ Magick::Image

    Parameters:

    • threshold (Numeric) —

      The threshold value, a number between 0 and QuantumRange.

    • *channels (Magick::ChannelType) —

      one or more ChannelType arguments.

Returns:



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# File 'ext/RMagick/rmimage.cpp', line 1466

VALUE
Image_bilevel_channel(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    ChannelType channels;
    double threshold;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
#endif

    image = rm_check_destroyed(self);
    channels = extract_channels(&argc, argv);

    if (argc > 1)
    {
        raise_ChannelType_error(argv[argc-1]);
    }
    if (argc == 0)
    {
        rb_raise(rb_eArgError, "no threshold specified");
    }

    threshold = NUM2DBL(argv[0]);
    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    BEGIN_CHANNEL_MASK(new_image, channels);
    GVL_STRUCT_TYPE(BilevelImage) args = { new_image, threshold, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(BilevelImage), &args);
    END_CHANNEL_MASK(new_image);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    GVL_STRUCT_TYPE(BilevelImageChannel) args = { new_image, channels, threshold };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(BilevelImageChannel), &args);
    rm_check_image_exception(new_image, DestroyOnError);
#endif

    return rm_image_new(new_image);
}