Method: Magick::Image#pixel_color

Defined in:

ext/RMagick/rmimage.cpp

#pixel_color(x, y) ⇒ Magick::Pixel #pixel_color(x, y, color) ⇒ Magick::Pixel

Get/set the color of the pixel at x, y.

Overloads:

• #pixel_color(x, y) ⇒ Magick::Pixel

  Get the color

  Parameters:

  • x (Numeric) —

    The x-coordinates of the pixel.

  • y (Numeric) —

    The y-coordinates of the pixel.

  Returns:

  • (Magick::Pixel) —

    the pixel at x, y.

• #pixel_color(x, y, color) ⇒ Magick::Pixel

  Set the color

  Parameters:

  • x (Numeric) —

    The x-coordinates of the pixel.

  • y (Numeric) —

    The y-coordinates of the pixel.

  • color (Magick::Pixel, String) —

    the color

  Returns:

  • (Magick::Pixel) —

    the old color at x, y.

# File 'ext/RMagick/rmimage.cpp', line 10620

VALUE
Image_pixel_color(int argc, VALUE *argv, VALUE self)
{
    Image *image;
    Pixel new_color;
    PixelPacket old_color;
    ExceptionInfo *exception;
    long x, y;
    unsigned int set = False;
    MagickBooleanType okay;
#if defined(IMAGEMAGICK_7)
    Quantum *pixel;
    const Quantum *old_pixel;
#else
    PixelPacket *pixel;
    const PixelPacket *old_pixel;
    MagickPixel mpp;
    IndexPacket *indexes;
#endif

    memset(&old_color, 0, sizeof(old_color));

    image = rm_check_destroyed(self);

    switch (argc)
    {
        case 3:
            rb_check_frozen(self);
            set = True;
            // Replace with new color? The arg can be either a color name or
            // a Magick::Pixel.
            Color_to_Pixel(&new_color, argv[2]);
        case 2:
            break;
        default:
            rb_raise(rb_eArgError, "wrong number of arguments (%d for 2 or 3)", argc);
            break;
    }

    x = NUM2LONG(argv[0]);
    y = NUM2LONG(argv[1]);

    // Get the color of a pixel
    if (!set)
    {
        exception = AcquireExceptionInfo();
        GVL_STRUCT_TYPE(GetVirtualPixels) args = { image, x, y, 1, 1, exception };
        void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(GetVirtualPixels), &args);
        old_pixel = reinterpret_cast<decltype(old_pixel)>(ret);
        CHECK_EXCEPTION();

        DestroyExceptionInfo(exception);

#if defined(IMAGEMAGICK_7)
        old_color.red   = GetPixelRed(image, old_pixel);
        old_color.green = GetPixelGreen(image, old_pixel);
        old_color.blue  = GetPixelBlue(image, old_pixel);
        old_color.alpha = GetPixelAlpha(image, old_pixel);
        old_color.black = GetPixelBlack(image, old_pixel);
        return Pixel_from_PixelPacket(&old_color);
#else
        old_color = *old_pixel;
        indexes = GetAuthenticIndexQueue(image);
        // PseudoClass
        if (image->storage_class == PseudoClass)
        {
            old_color = image->colormap[(unsigned long)*indexes];
        }
        if (!image->matte)
        {
            old_color.opacity = OpaqueOpacity;
        }

        rm_init_magickpixel(image, &mpp);
        mpp.red = GetPixelRed(&old_color);
        mpp.green = GetPixelGreen(&old_color);
        mpp.blue = GetPixelBlue(&old_color);
        mpp.opacity = GetPixelOpacity(&old_color);
        if (indexes)
        {
            mpp.index = GetPixelIndex(indexes);
        }
        return Pixel_from_MagickPixel(&mpp);
#endif
    }

    // ImageMagick segfaults if the pixel location is out of bounds.
    // Do what IM does and return the background color.
    if (x < 0 || y < 0 || (unsigned long)x >= image->columns || (unsigned long)y >= image->rows)
    {
        return Pixel_from_PixelColor(&image->background_color);
    }

#if defined(IMAGEMAGICK_7)
    exception = AcquireExceptionInfo();
#endif

    if (image->storage_class == PseudoClass)
    {
#if defined(IMAGEMAGICK_7)
        GVL_STRUCT_TYPE(SetImageStorageClass) args = { image, DirectClass, exception };
        void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(SetImageStorageClass), &args);
        okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
        CHECK_EXCEPTION();
        if (!okay)
        {
            DestroyExceptionInfo(exception);
            rb_raise(Class_ImageMagickError, "SetImageStorageClass failed. Can't set pixel color.");
        }
#else
        GVL_STRUCT_TYPE(SetImageStorageClass) args = { image, DirectClass };
        void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(SetImageStorageClass), &args);
        okay = static_cast<MagickBooleanType>(reinterpret_cast<intptr_t &>(ret));
        rm_check_image_exception(image, RetainOnError);
        if (!okay)
        {
            rb_raise(Class_ImageMagickError, "SetImageStorageClass failed. Can't set pixel color.");
        }
#endif
    }

#if defined(IMAGEMAGICK_6)
    exception = AcquireExceptionInfo();
#endif

    GVL_STRUCT_TYPE(GetAuthenticPixels) args = { image, x, y, 1, 1, exception };
    void *ret = CALL_FUNC_WITHOUT_GVL(GVL_FUNC(GetAuthenticPixels), &args);
    pixel = reinterpret_cast<decltype(pixel)>(ret);
    CHECK_EXCEPTION();

    if (pixel)
    {
#if defined(IMAGEMAGICK_7)
        old_color.red   = GetPixelRed(image, pixel);
        old_color.green = GetPixelGreen(image, pixel);
        old_color.blue  = GetPixelBlue(image, pixel);
        old_color.alpha = GetPixelAlpha(image, pixel);
        old_color.black = GetPixelBlack(image, pixel);

        SetPixelRed(image,   new_color.red,   pixel);
        SetPixelGreen(image, new_color.green, pixel);
        SetPixelBlue(image,  new_color.blue,  pixel);
        SetPixelAlpha(image, new_color.alpha, pixel);
        SetPixelBlack(image, new_color.black, pixel);
#else
        old_color = *pixel;
        indexes = GetAuthenticIndexQueue(image);
        if (!image->matte)
        {
            old_color.opacity = OpaqueOpacity;
        }

        SetPixelRed(pixel,     new_color.red);
        SetPixelGreen(pixel,   new_color.green);
        SetPixelBlue(pixel,    new_color.blue);
        SetPixelOpacity(pixel, new_color.opacity);
        if (indexes)
        {
            SetPixelIndex(indexes, new_color.black);
        }
#endif

        GVL_STRUCT_TYPE(SyncAuthenticPixels) args = { image, exception };
        CALL_FUNC_WITHOUT_GVL(GVL_FUNC(SyncAuthenticPixels), &args);
        CHECK_EXCEPTION();
    }

    DestroyExceptionInfo(exception);

    return Pixel_from_PixelPacket(&old_color);
}