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Avoid backing store color space conversions.

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We want the Qt backing store to be in the device color
space by default. This will avoid colour space conversions
when blitting it to screen, at the cost of a potential 
loss in color accuracy.

As it turns out, CGColorSpaceCreateDeviceRGB no longer
crates a device color space but rather a generic color
space. (Since 10.4). Create the color space with a system
profile instead.

Accurate color representation needs to be supported
at some point, but this fast path should be the
default.

Change-Id: I7ebb77b36f81f66119d8c2ef464723401ec1d1e8
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
This commit is contained in:
Morten Johan Sorvig 2012-12-04 15:19:27 +01:00 committed by The Qt Project
parent 2f6e967eb7
commit 9650a5aa25
1 changed files with 15 additions and 1 deletions
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16
src/plugins/platforms/cocoa/qcocoahelpers.mm
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@ -789,7 +789,21 @@ CGImageRef qt_mac_toCGImage(const QImage &qImage, bool isMask, uchar **dataCopy)
NULL,
false);
} else {
CGColorSpaceRef cgColourSpaceRef = CGColorSpaceCreateDeviceRGB();
// Try get a device color space. Using the device color space means
// that the CGImage can be drawn to screen without per-pixel color
// space conversion, at the cost of less color accuracy.
CGColorSpaceRef cgColourSpaceRef = 0;
CMProfileRef sysProfile;
if (CMGetSystemProfile(&sysProfile) == noErr)
{
cgColourSpaceRef = CGColorSpaceCreateWithPlatformColorSpace(sysProfile);
CMCloseProfile(sysProfile);
}
// Fall back to Generic RGB if a profile was not found.
if (!cgColourSpaceRef)
cgColourSpaceRef = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
cgImage = CGImageCreate(width,
height,
colorBufferSize,