[Webkit-unassigned] [Bug 43962] Improve FEGaussianBlur algorithm performance

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=43962





--- Comment #3 from Ariya Hidayat <ariya.hidayat at gmail.com>  2010-08-13 09:16:38 PST ---
(From update of attachment 64318)
This looks good! :)

>  #include "GraphicsContext.h"
>  #include "ImageData.h"
>  #include <wtf/MathExtras.h>

Needs the Sencha copyright (see also Patch 2 in https://bugs.webkit.org/show_bug.cgi?id=34479).

> +#define CURRENT_ALGO 0

Have you profiled the different between using CURRENT_ALGO and not using it?

> +// Note: image must be RGB32 format
> +static void blurHorizontal(unsigned char* image, int imgWidth, int imgHeight, int strideLine, int radius, bool swap = false)

The comment does not apply anymore since you prepare 'image' manually by yourself (hence, you know it's guaranteed RGB32 :)

> +    OwnPtr<ImageBuffer> tmpImageBuffer = ImageBuffer::create(resultImage()->size());
> +
> +    AffineTransform transform;
> +    transform.rotate(90);
> +    RefPtr<Pattern> pattern = Pattern::create(m_in->resultImage()->image(), false, false);
> +    tmpImageBuffer->context()->concatCTM(transform);
> +    tmpImageBuffer->context()->translate(0, -imageRect.height());
> +    tmpImageBuffer->context()->setFillPattern(pattern.get());
> +    tmpImageBuffer->context()->fillRect(imageRect);

This works only if every platform graphics stack supports fast 90 degree rotation (aka transposed). Qt supports this hence why I use it.
Otherwise, it is faster to transpose the pixels ourselves.

Possible idea: provide a default ImageBuffer::transpose and let the platform overrides it if it has a faster version.

BTW, track also Hyatt's refactoring on Canvas. This might or might not conflict with some of his changes, but just in case. https://bugs.webkit.org/show_bug.cgi?id=43507

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