Method: Magick::Image#posterize

Defined in:
ext/RMagick/rmimage.cpp

#posterize(levels = 4, dither = false) ⇒ Object

Reduces the image to a limited number of colors for a “poster” effect.

Returns a new image.

Parameters:

  • levels (Numeric) (defaults to: 4) —

    number of input arguments

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

    array of input arguments

Returns:

  • a new image



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# File 'ext/RMagick/rmimage.cpp', line 10886

VALUE
Image_posterize(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    MagickBooleanType dither = MagickFalse;
    unsigned long levels = 4;
#if defined(IMAGEMAGICK_7)
    DitherMethod dither_method;
    ExceptionInfo *exception;
#endif

    image = rm_check_destroyed(self);
    switch (argc)
    {
        case 2:
            dither = (MagickBooleanType) RTEST(argv[1]);
            /* fall through */
        case 1:
            levels = NUM2ULONG(argv[0]);
            /* fall through */
        case 0:
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 0 to 2)", argc);
    }

    new_image = rm_clone_image(image);

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
    dither_method = dither ? RiemersmaDitherMethod : NoDitherMethod;
    GVL_STRUCT_TYPE(PosterizeImage) args = { new_image, levels, dither_method, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(PosterizeImage), &args);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);
#else
    GVL_STRUCT_TYPE(PosterizeImage) args = { new_image, levels, dither };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(PosterizeImage), &args);
    rm_check_image_exception(new_image, DestroyOnError);
#endif

    return rm_image_new(new_image);
}