Method: Magick::Image#quantize

Defined in:
ext/RMagick/rmimage.cpp

#quantize(number_colors = 256, colorspace = Magick::RGBColorspace, dither = true, tree_depth = 0, measure_error = false) ⇒ Magick::Image

Analyzes the colors within a reference image and chooses a fixed number of colors to represent the image. The goal of the algorithm is to minimize the difference between the input and output image while minimizing the processing time.

Returns a new image.

Parameters:

  • number_colors (Numeric) (defaults to: 256) —

    The maximum number of colors in the result image.

  • colorspace (Magick::ColorspaceType) (defaults to: Magick::RGBColorspace) —

    The colorspace to quantize in.

  • dither (Boolean) (defaults to: true) —

    If true, Magick::RiemersmaDitherMethod will be used as DitherMethod. otherwise NoDitherMethod.

  • tree_depth (Numeric) (defaults to: 0) —

    The tree depth to use while quantizing. The values 0 and 1 support automatic tree depth determination. The tree depth may be forced via values ranging from 2 to

    1. The ideal tree depth depends on the characteristics of the input image, and may be

    determined through experimentation.

  • measure_error (Boolean) (defaults to: false) —

    Set to true to calculate quantization errors when quantizing the image.

Returns:



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# File 'ext/RMagick/rmimage.cpp', line 11231

VALUE
Image_quantize(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    QuantizeInfo quantize_info;
#if defined(IMAGEMAGICK_7)
    ExceptionInfo *exception;
#endif

    image = rm_check_destroyed(self);
    GetQuantizeInfo(&quantize_info);

    switch (argc)
    {
        case 5:
            quantize_info.measure_error = (MagickBooleanType) RTEST(argv[4]);
        case 4:
            quantize_info.tree_depth = NUM2UINT(argv[3]);
        case 3:
            if (rb_obj_is_kind_of(argv[2], Class_DitherMethod))
            {
                VALUE_TO_ENUM(argv[2], quantize_info.dither_method, DitherMethod);
#if defined(IMAGEMAGICK_6)
                quantize_info.dither = (MagickBooleanType)(quantize_info.dither_method != NoDitherMethod);
#endif
            }
            else
            {
#if defined(IMAGEMAGICK_7)
                quantize_info.dither_method = RTEST(argv[2]) ? RiemersmaDitherMethod : NoDitherMethod;
#else
                quantize_info.dither = (MagickBooleanType) RTEST(argv[2]);
#endif
            }
        case 2:
            VALUE_TO_ENUM(argv[1], quantize_info.colorspace, ColorspaceType);
        case 1:
            quantize_info.number_colors = NUM2UINT(argv[0]);
        case 0:
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 0 to 5)", argc);
            break;
    }

    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    GVL_STRUCT_TYPE(QuantizeImage) args = { &quantize_info, new_image, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(QuantizeImage), &args);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    GVL_STRUCT_TYPE(QuantizeImage) args = { &quantize_info, new_image };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(QuantizeImage), &args);
    rm_check_image_exception(new_image, DestroyOnError);
#endif

    return rm_image_new(new_image);
}