Method: Magick::Image#levelize_channel

Defined in:
ext/RMagick/rmimage.cpp

#levelize_channel(black_point, white_point = Magick::QuantumRange-black_point, gamma = 1.0, channel = Magick::AllChannels) ⇒ Magick::Image #levelize_channel(black_point, white_point = Magick::QuantumRange-black_point, gamma = 1.0, *channels) ⇒ Magick::Image

Maps black and white to the specified points. The reverse of #level_channel.

Overloads:

  • #levelize_channel(black_point, white_point = Magick::QuantumRange-black_point, gamma = 1.0, channel = Magick::AllChannels) ⇒ Magick::Image

    Parameters:

    • black (Numeric) —

      A black point level in the range 0..QuantumRange.

    • white (Numeric) —

      A white point level in the range 0..QuantumRange.

    • gamma (Numeric) (defaults to: 1.0) —

      A gamma correction in the range 0.0 - 10.0.

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

      a ChannelType arguments.

  • #levelize_channel(black_point, white_point = Magick::QuantumRange-black_point, gamma = 1.0, *channels) ⇒ Magick::Image

    Parameters:

    • black (Numeric) —

      A black point level in the range 0..QuantumRange.

    • white (Numeric) —

      A white point level in the range 0..QuantumRange.

    • gamma (Numeric) (defaults to: 1.0) —

      A gamma correction in the range 0.0 - 10.0.

    • *channels (Magick::ChannelType) —

      one or more ChannelType arguments.

Returns:



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# File 'ext/RMagick/rmimage.cpp', line 8718

VALUE
Image_levelize_channel(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    ChannelType channels;
    double black_point, white_point;
    double gamma = 1.0;
    MagickBooleanType okay;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
#endif

    image = rm_check_destroyed(self);
    channels = extract_channels(&argc, argv);
    if (argc > 3)
    {
        raise_ChannelType_error(argv[argc-1]);
    }

    switch (argc)
    {
        case 3:
            gamma = NUM2DBL(argv[2]);
        case 2:
            white_point = NUM2DBL(argv[1]);
            black_point = NUM2DBL(argv[0]);
            break;
        case 1:
            black_point = NUM2DBL(argv[0]);
            white_point = QuantumRange - black_point;
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 1 or more)", argc);
            break;
    }

    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    BEGIN_CHANNEL_MASK(new_image, channels);
    GVL_STRUCT_TYPE(LevelizeImage) args = { new_image, black_point, white_point, gamma, exception };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(LevelizeImage), &args);
    okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
    END_CHANNEL_MASK(new_image);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    GVL_STRUCT_TYPE(LevelizeImageChannel) args = { new_image, channels, black_point, white_point, gamma };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(LevelizeImageChannel), &args);
    okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
    rm_check_image_exception(new_image, DestroyOnError);
#endif

    if (!okay)
    {
        rb_raise(rb_eRuntimeError, "LevelizeImageChannel failed for unknown reason.");
    }
    return rm_image_new(new_image);
}