Method: Magick::Image#level2

Defined in:
ext/RMagick/rmimage.cpp

#level2(black_point = 0.0, white_point = Magick::QuantumRange, gamma = 1.0) ⇒ Magick::Image

Adjusts the levels of an image by scaling the colors falling between specified white and black points to the full available quantum range.

Returns a new image.

Parameters:

  • black_point (Numeric) (defaults to: 0.0) —

    A black point level in the range 0 - QuantumRange.

  • white_point (Numeric) (defaults to: Magick::QuantumRange) —

    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.

Returns:



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# File 'ext/RMagick/rmimage.cpp', line 8492

VALUE
Image_level2(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    double black_point = 0.0, gamma_val = 1.0, white_point = (double)QuantumRange;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
#else
    char level[50];
#endif

    image = rm_check_destroyed(self);
    switch (argc)
    {
        case 0:             // take all the defaults
            break;
        case 1:
            black_point = NUM2DBL(argv[0]);
            white_point = QuantumRange - black_point;
            break;
        case 2:
            black_point = NUM2DBL(argv[0]);
            white_point = NUM2DBL(argv[1]);
            break;
        case 3:
            black_point = NUM2DBL(argv[0]);
            white_point = NUM2DBL(argv[1]);
            gamma_val   = NUM2DBL(argv[2]);
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 0 to 3)", argc);
            break;
    }

    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    GVL_STRUCT_TYPE(LevelImage) args = { new_image, black_point, white_point, gamma_val, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(LevelImage), &args);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    snprintf(level, sizeof(level), "%gx%g+%g", black_point, white_point, gamma_val);
    GVL_STRUCT_TYPE(LevelImage) args = { new_image, level };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(LevelImage), &args);
    rm_check_image_exception(new_image, DestroyOnError);
#endif

    return rm_image_new(new_image);
}