Method: Magick::Image#export_pixels

Defined in:

ext/RMagick/rmimage.cpp

#export_pixels(x = 0, y = 0, cols = self.columns, rows = self.rows, map = "RGB") ⇒ Array<Numeric>

Extracts the pixel data from the specified rectangle and returns it as an array of Integer values. The array returned by #export_pixels is suitable for use as an argument to #import_pixels.

Returns array of pixels.

Parameters:

• x (Numeric) (defaults to: 0) —

  The offset of the rectangle from the upper-left corner of the image.

• y (Numeric) (defaults to: 0) —

  The offset of the rectangle from the upper-left corner of the image.

• cols (Numeric) (defaults to: self.columns) —

  The width of the rectangle.

• rows (Numeric) (defaults to: self.rows) —

  The height of the rectangle.

• map (String) (defaults to: "RGB") —

  A string that describes which pixel channel data is desired and the order in which it should be stored. It can be any combination or order of R = red, G = green, B = blue, A = alpha, C = cyan, Y = yellow, M = magenta, K = black, I = intensity (for grayscale), or P = pad.

Returns:

• (Array<Numeric>) —

  array of pixels

# File 'ext/RMagick/rmimage.cpp', line 6610

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;
    MagickBooleanType okay;
    const char *map = "RGB";
    Quantum *pixels;
    VALUE ary;
    ExceptionInfo *exception;


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

    switch (argc)
    {
        case 5:
            map   = StringValueCStr(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 0 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);
    }

    exception = AcquireExceptionInfo();

    GVL_STRUCT_TYPE(ExportImagePixels) args = { image, x_off, y_off, cols, rows, map, QuantumPixel, (void *)pixels, exception };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(ExportImagePixels), &args);
    okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
    if (!okay)
    {
        xfree((void *)pixels);
        CHECK_EXCEPTION();

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

    DestroyExceptionInfo(exception);

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

    xfree((void *)pixels);

    RB_GC_GUARD(ary);

    return ary;
}