[OpenJDK 2D-Dev] [10] RFR JDK-8176795: Wrong color drawn when painting translucent colors on volatile images using XRender.

[Jayathirth D V]

Hello All,

 

Gentle reminder for review.

 

Thanks,

Jay

 

From: Jayathirth D V 
Sent: Thursday, December 07, 2017 8:47 PM
To: 2d-dev
Subject: [OpenJDK 2D-Dev] [10] RFR JDK-8176795: Wrong color drawn when painting translucent colors on volatile images using XRender.

 

Hello All,

 

Please review the following fix in JDK10 :

 

Bug : https://bugs.openjdk.java.net/browse/JDK-8176795 

Webrev : http://cr.openjdk.java.net/~jdv/8176795/webrev.00/ 

 

Issue : When we draw translucent color over an opaque color in Unix from JDK 8 we get different color after composition compared to any other platform.

 

Root cause : From JDK 8, X Rendering extension is enabled in Unix and we see this problem only when we use XRender in Unix if we use GLX or  X11 we don't see any issue.  Also X Rendering extension expects pre-multiplied alpha color values, so we need to convert the non-premultiplied alpha color values to pre-multiplied alpha color values before give pixel value to XRender for drawing. The main problem is we do this operation of conversion twice:

1)      When we call Graphics2D.setColor() it uses ArgbPre PixelConverter based on SurfaceData(here it is XRenderPixMap ArgbPre surface) and converts the color to pre-multiplied values.

2)      When we call Graphics2D.fillRect() internally before we compose the destination(opaque color) and source(translucent color) we prepare source render rectangle for X Render extension. Here again we convert the already converted color values to premultiplied values. 

 

Solution : There is no need for us to do non-pre to pre color conversion again at XRender level so it should be removed. Also this logic of non-pre to pre color conversion at XRender was only used when source is Solid color and not Texture/Gradient. So I have completely removed this logic itself as it not needed anywhere else.

 

Thanks,

Jay

 
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