The explanation sounds reasonable, although I'd like to give Clemens a
chance to review this.
-phil.
On 12/07/2017 07:16 AM, Jayathirth D V wrote:
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/
<http://cr.openjdk.java.net/%7Ejdv/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
