[Spice-devel] [PATCH spice-html5]Handling non top-down lz_rgb

[Jeremy White]

Hi Vincent,

> +function flip_image_data(img)
> +{
> +    var w = img.width;
> +    var h = img.height;
> +    var temp_w = w;
> +    var temp_h = h;
> +    var buff = new Uint8Array(img.width * img.height * 4);
> +    while (temp_h--)
> +    {
> +        while (temp_w--)
> +        {
> +            buff[(temp_h * w + temp_w) * 4] = img.data[((h - temp_h -
> 1) * w + temp_w) * 4];
> +            buff[(temp_h * w + temp_w) * 4 + 1] = img.data[((h - temp_h
> - 1) * w + temp_w) * 4 + 1];
> +            buff[(temp_h * w + temp_w) * 4 + 2] = img.data[((h - temp_h
> - 1) * w + temp_w) * 4 + 2];
> +            buff[(temp_h * w + temp_w) * 4 + 3] = img.data[((h - temp_h
> - 1) * w + temp_w) * 4 + 3];
> +        }
> +        temp_w = w;
> +    }
> +    img.data.set(buff);

Couldn't this be done more simply by swapping line by line, rather than
pixel by pixel?  If I'm not mistaken, the Uint8Array set() method will
take an array and offset as a parameter, and you can get a subarray
fairly easily.  I have no idea if that will provide a performance boost,
but it will least enable the Javascript engines to try.

Either way, if you could resubmit this as a discrete git-format-patch
entry (probably with signed-off-by while you're at it), I'd appreciate it.

Cheers,

Jeremy