Bug 134513 – [iOS] Subsampled JPEG images do not draw correctly via the canvas APIs

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Dean Jackson]

[iOS] Subsampled JPEG images do not draw correctly via the canvas APIs

[Dean Jackson]

Created attachment 234200 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 234200 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=234200&action=review

> Source/WebCore/platform/graphics/cg/BitmapImageCG.cpp:206
> +    if (m_originalSize.width() && m_originalSize.height())
> +        scaledSrcRect.scale(m_size.width() / static_cast<float>(m_originalSize.width()), m_size.height() / static_cast<float>(m_originalSize.height()));

Don't we have a subsampling scale (m_scale) for each frame already?

> Source/WebCore/platform/graphics/cg/GraphicsContext3DCG.cpp:340
> +                scaleHint = std::min<float>(1.0f, std::max(m_image->size().width() / originalSize.width(), m_image->size().width() / originalSize.height()));

Image knows the scale already?

[Dean Jackson]

Comment on attachment 234200 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=234200&action=review

>> Source/WebCore/platform/graphics/cg/BitmapImageCG.cpp:206
>> +        scaledSrcRect.scale(m_size.width() / static_cast<float>(m_originalSize.width()), m_size.height() / static_cast<float>(m_originalSize.height()));
> 
> Don't we have a subsampling scale (m_scale) for each frame already?

No, we might not have any frames yet. Later in this method we call frameAtIndex to generate the frame for the subsample.

>> Source/WebCore/platform/graphics/cg/GraphicsContext3DCG.cpp:340
>> +                scaleHint = std::min<float>(1.0f, std::max(m_image->size().width() / originalSize.width(), m_image->size().width() / originalSize.height()));
> 
> Image knows the scale already?

Same as above, and even if it did, I would have to make the frames public just for this.

[Dean Jackson]

I changed FrameData::m_scale to m_subsamplingScale though.

[Tim Horton]

Comment on attachment 234200 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=234200&action=review

> Source/WebCore/platform/graphics/cg/BitmapImageCG.cpp:202
> +    FloatRect scaledSrcRect = srcRect;

<channeling ben> scaled into what coordinate space

[Dean Jackson]

        <rdar://problem/12078860>
        <rdar://problem/16745393>

[Dean Jackson]

Committed r170675: <http://trac.webkit.org/changeset/170675>