Method: Magick::Image#export_pixels

Defined in:

ext/RMagick/rmimage.c

#export_pixels(*args) ⇒ Object

Extract image pixels in the form of an array.

Ruby usage:

- @verbatim Image#export_pixels @endverbatim
- @verbatim Image#export_pixels(x) @endverbatim
- @verbatim Image#export_pixels(x, y) @endverbatim
- @verbatim Image#export_pixels(x, y, cols) @endverbatim
- @verbatim Image#export_pixels(x, y, cols, rows) @endverbatim
- @verbatim Image#export_pixels(x, y, cols, rows, map) @endverbatim

Notes:

- Default x is 0
- Default y is 0
- Default cols is self.columns
- Default rows is self.rows
- Default map is "RGB"

Parameters:

• argc —

  number of input arguments

• argv —

  array of input arguments

• self —

  this object

Returns:

• array of pixels

# File 'ext/RMagick/rmimage.c', line 5796

VALUE
Image_export_pixels(int argc, VALUE *argv, VALUE self)
{
    Image *image;
    long x_off = 0L, y_off = 0L;
    unsigned long cols, rows;
    long n, npixels;
    unsigned int okay;
    const char *map = "RGB";
    Quantum *pixels;
    volatile VALUE ary;
    ExceptionInfo exception;


    image = rm_check_destroyed(self);
    cols = image->columns;
    rows = image->rows;

    switch (argc)
    {
        case 5:
            map   = StringValuePtr(argv[4]);
        case 4:
            rows  = NUM2ULONG(argv[3]);
        case 3:
            cols  = NUM2ULONG(argv[2]);
        case 2:
            y_off = NUM2LONG(argv[1]);
        case 1:
            x_off = NUM2LONG(argv[0]);
        case 0:
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 1 to 5)", argc);
            break;
    }

    if (   x_off < 0 || (unsigned long)x_off > image->columns
           || y_off < 0 || (unsigned long)y_off > image->rows
           || cols == 0 || rows == 0)
    {
        rb_raise(rb_eArgError, "invalid extract geometry");
    }


    npixels = (long)(cols * rows * strlen(map));
    pixels = ALLOC_N(Quantum, npixels);
    if (!pixels)    // app recovered from exception
    {
        return rb_ary_new2(0L);
    }

    GetExceptionInfo(&exception);

    okay = ExportImagePixels(image, x_off, y_off, cols, rows, map, QuantumPixel, (void *)pixels, &exception);
    if (!okay)
    {
        xfree((void *)pixels);
        CHECK_EXCEPTION()

        // Should never get here...
        rm_magick_error("ExportImagePixels failed with no explanation.", NULL);
    }

    (void) DestroyExceptionInfo(&exception);

    ary = rb_ary_new2(npixels);
    for (n = 0; n < npixels; n++)
    {
        (void) rb_ary_push(ary, QUANTUM2NUM(pixels[n]));
    }

    xfree((void *)pixels);

    return ary;
}