Method: Magick::Image#function_channel

Defined in:

ext/RMagick/rmimage.cpp

#function_channel(function, *args, channel = Magick::AllChannels) ⇒ Magick::Image #function_channel(function, *args, *channels) ⇒ Magick::Image

Set the function on a channel.

Overloads:

• #function_channel(function, *args, channel = Magick::AllChannels) ⇒ Magick::Image

  Parameters:

  • function (Magick::MagickFunction) —

    the function

  • *args (Numeric) —

    One or more floating-point numbers. The number of parameters depends on the function. See the ImageMagick documentation for details.

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

    a ChannelType arguments.

• #function_channel(function, *args, *channels) ⇒ Magick::Image

  Parameters:

  • function (Magick::MagickFunction) —

    the function

  • *args (Numeric) —

    One or more floating-point numbers. The number of parameters depends on the function. See the ImageMagick documentation for details.

  • *channels (Magick::ChannelType) —

    one or more ChannelType arguments.

Returns:

• (Magick::Image) —

  a new image

See Also:

• https://www.imagemagick.org/script/command-line-options.php#function

# File 'ext/RMagick/rmimage.cpp', line 7333

VALUE
Image_function_channel(int argc, VALUE *argv, VALUE self)
{
    Image *image, *new_image;
    MagickFunction function;
    unsigned long n, nparms;
    double *parms;
    ChannelType channels;
    ExceptionInfo *exception;

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

    // The number of parameters depends on the function.
    if (argc == 0)
    {
        rb_raise(rb_eArgError, "no function specified");
    }

    VALUE_TO_ENUM(argv[0], function, MagickFunction);
    argc -= 1;
    argv += 1;

    switch (function)
    {
        case PolynomialFunction:
            if (argc == 0)
            {
                rb_raise(rb_eArgError, "PolynomialFunction requires at least one argument.");
            }
            break;
        case SinusoidFunction:
        case ArcsinFunction:
        case ArctanFunction:
           if (argc < 1 || argc > 4)
           {
               rb_raise(rb_eArgError, "wrong number of arguments (%d for 1 to 4)", argc);
           }
           break;
        default:
            rb_raise(rb_eArgError, "undefined function");
            break;
    }

    nparms = argc;
    parms = ALLOC_N(double, nparms);

    for (n = 0; n < nparms; n++)
    {
        VALUE element = argv[n];
        if (rm_check_num2dbl(element))
        {
            parms[n] = NUM2DBL(element);
        }
        else
        {
            xfree(parms);
            rb_raise(rb_eTypeError, "type mismatch: %s given", rb_class2name(CLASS_OF(element)));
        }
    }

    exception = AcquireExceptionInfo();
    new_image = rm_clone_image(image);
#if defined(IMAGEMAGICK_7)
    BEGIN_CHANNEL_MASK(new_image, channels);
    GVL_STRUCT_TYPE(FunctionImage) args = { new_image, function, nparms, parms, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(FunctionImage), &args);
    END_CHANNEL_MASK(new_image);
#else
    GVL_STRUCT_TYPE(FunctionImageChannel) args = { new_image, channels, function, nparms, parms, exception };
    CALL_FUNC_WITHOUT_GVL(GVL_FUNC(FunctionImageChannel), &args);
#endif
    xfree(parms);
    rm_check_exception(exception, new_image, DestroyOnError);
    DestroyExceptionInfo(exception);

    return rm_image_new(new_image);
}