Bug 26037 – [Skia] Canvas globalAlpha property not applied to drawImage method

• Component: Platform
• Status: RESOLVED FIXED

[Anand K. Mistry]

Setting the globalImage property of a canvas context is not honoured when doing a drawImage. Test case available at:
http://philip.html5.org/tests/canvas/suite/tests/2d.composite.globalAlpha.image.html

Chromium bug http://code.google.com/p/chromium/issues/detail?id=5281

Tested on:
Firefox 3.0 Linux - PASS
Firefox 3.5b4 OSX - PASS
WebKit nightly OSX (44174) - PASS
Chromium SVN (16864) - FAIL

[Dirk Schulze]

We fixexd it on Cairo by reading and applying the globalAlpha in WebCore/platform/graphics/cairo/ImageCairo.cpp directly. We added getAlpha() for Cairo to GraphicsContext.h maybe Skia needs to use it too.

[Anand K. Mistry]

Created attachment 30889 [details]
Use the alpha channel when painting images in skia.

[Anand K. Mistry]

The patch is by me.  Please ignore the gmail address.

[Dimitri Glazkov (Google)]

Comment on attachment 30889 [details]
Use the alpha channel when painting images in skia.

> +    int alpha = roundf(platformContext->getAlpha() * 256);
> +    if (alpha > 255)
> +      alpha = 255;
> +    else if (alpha < 0)
> +      alpha = 0;
> +    paint.setAlpha(alpha);

4 spaces indent.

Looks great otherwise.

[Anand K. Mistry]

Created attachment 30929 [details]
Use the alpha channel when painting images in skia. Updated.

Changes:
Changed to 4 space indent.

[Dimitri Glazkov (Google)]

Comment on attachment 30929 [details]
Use the alpha channel when painting images in skia. Updated.

Don't forget to mark for review next time :)

[Dimitri Glazkov (Google)]

Landed as http://trac.webkit.org/changeset/44537.