Method: Magick::Image#function_channel

Defined in:
ext/RMagick/rmimage.c

#function_channel(*args) ⇒ Object

Set the function on a channel.

Ruby usage:

 - @verbatim Image#function_channel(function, args) @endverbatim
 - @verbatim Image#function_channel(function, args, channel) @endverbatim
 - @verbatim Image#function_channel(function, args, channel, ...) @endverbatim

Notes:
  - Default channel is AllChannels

Parameters:

  • argc —

    number of input arguments

  • argv —

    array of input arguments

  • self —

    this object

Returns:

  • a new image



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# File 'ext/RMagick/rmimage.c', line 6581

VALUE
Image_function_channel(int argc, VALUE *argv, VALUE self)
{
#if defined(HAVE_FUNCTIONIMAGECHANNEL)
    Image *image, *new_image;
    MagickFunction function;
    unsigned long n, nparms;
    volatile double *parameters;
    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)
    {
#if defined(HAVE_ENUM_POLYNOMIALFUNCTION)
        case PolynomialFunction:
            if (argc == 0)
            {
                rb_raise(rb_eArgError, "PolynomialFunction requires at least one argument.");
            }
            break;
#endif
#if defined(HAVE_ENUM_SINUSOIDFUNCTION)
        case SinusoidFunction:
#endif
#if defined(HAVE_ENUM_ARCSINFUNCTION)
        case ArcsinFunction:
#endif
#if defined(HAVE_ENUM_ARCTANFUNCTION)
        case ArctanFunction:
#endif
           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;
    parameters = parms = ALLOC_N(double, nparms);

    for (n = 0; n < nparms; n++)
    {
        parms[n] = NUM2DBL(argv[n]);
    }

    GetExceptionInfo(&exception);
    new_image = rm_clone_image(image);
    (void) FunctionImageChannel(new_image, channels, function, nparms, parms, &exception);
    (void) xfree(parms);
    rm_check_exception(&exception, new_image, DestroyOnError);
    DestroyExceptionInfo(&exception);

    return rm_image_new(new_image);
#else
    rm_not_implemented();
    return (VALUE)0;
    argc = argc;
    argv = argv;
    self = self;
#endif
}