The performance of QPainter::drawImage

glacierx

Dear all,

Currently Im porting an application written with QT 4.8 on windows into mac os x. I found the performance of QPainter::drawImage differs dramatically on mac os x and windows.

After I googled a bunch of articles and profile my qt application on mac, I found the reason is that the mac version drawImage was implemented by calling Quartz function CGContextDrawImage which consequently calls argb32_sample_argb32. argb32_sample_argb32 wastes most of the cpu cycles.

Most probably, mac os x convert generic color space into device-dependent color space in the API CGContextDrawImage. However I modified the source code of QT 4.8 the obtain the system display color space directly.

The result is still not good. My mac version app is significantly slower than windows version.

Anyone can tell me why?

@
/// QT 4.8's source code modified by me

CGColorSpaceRef QCoreGraphicsPaintEngine::macGenericColorSpace()
{

#if 0
if (!m_genericColorSpace) {
#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_4) {
m_genericColorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
} else
#endif
{
m_genericColorSpace = CGColorSpaceCreateDeviceRGB();
}
if (!m_postRoutineRegistered) {
m_postRoutineRegistered = true;
qAddPostRoutine(QCoreGraphicsPaintEngine::cleanUpMacColorSpaces);
}
}
return m_genericColorSpace;
#else
// Just return the main display colorspace for the moment.
// return macDisplayColorSpace();
return CreateSystemColorSpace();
#endif
}

CGColorSpaceRef CreateSystemColorSpace () {
CMProfileRef sysprof = NULL;
CGColorSpaceRef dispColorSpace = NULL;

// Get the Systems Profile for the main display
if (CMGetSystemProfile(&sysprof) == noErr)
{
// Create a colorspace with the systems profile
dispColorSpace = CGColorSpaceCreateWithPlatformColorSpace(sysprof);

  // Close the profile                                                                                                                                                                                                                                                      
  CMCloseProfile(sysprof&#41;;
}

return dispColorSpace;
}
@

[EDIT: code formatting, please wrap in @-tags, Volker]

koahnig

Welcome to devnet

You need to embrace your code section with '@' "(See also)":http://developer.qt.nokia.com/wiki/ForumHelp#e3f82045ad0f480d3fb9e0ac2d58fb01
Otherwise it is unreadable. You can edit your post with the link below your name.

qttester5

Did you ever get to the bottom of this?