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Old 01-Sep-2017, 15:47
tony.yutian tony.yutian is offline
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setWorldTransform giving me trouble!

Hello everybody, I am running into a very weird issue.

I need to draw in memory and then read the buffer from the picture and write to a display device. It was working all fine until 1 day I need to use setWorldTransform in a different memory picture, and the world start turning weird.

Below is the test code I have. You can simply copy all to a empty application, and call this function anywhere.
CPP / C++ / C Code:
void TestCImage()
	CRect rectWhere(5, 5, 10, 10);
	CImage img1, img2;
	CDC *pDC1, *pDC2;
	CBrush brush;
	XFORM xf1 = { 1.0, 0.0, 0.0, 1.0, 0.0, 0.0 };
	XFORM xf2 = { 1.1, 0.0, 0.0, 1.1, 0.0, 0.0 };
	XFORM xf3 = { 1.001, 0.0, 0.0, 1.001, 0.0, 0.0 };


	img1.Create(200, 200, 32);
	pDC1 = CDC::FromHandle(img1.GetDC());
	pDC1->SetWorldTransform(&xf2); //this is the weird part. xf1 and xf3 will be fine. xf2 cause the trouble. but, but, but! how would any settings on img1 and pDC1 affect the result in img2??????? they are totally in different variable ok???? and I did not do anything after I call SetWorldTransform???


	img2.Create(20, 20, 32);
	pDC2 = CDC::FromHandle(img2.GetDC());
	pDC2->FillRect(rectWhere, &brush);

	COLORREF* color = (COLORREF*)img2.GetPixelAddress(rectWhere.left,;
	TRACE("\nValue is %X\n", color[0]);      //suppose to be AAAAAA, if use xf2 in the SetWorldTransform, this value will become 0.

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