Qpainter draws text with gray edge on qimage

When I try to use qpainter to draw text on qimage, I use the default compositionmode_ Source over mode, but there are some gray edges around the text. However, when I drew on qpixmap instead, the text I drew was the same as I expected. For specific comparison, please refer to the appendix.

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According to Jensen's description, I used a demo to reproduce this problem, just like the effect of the newly added image. The newly added zip package is a duplicate demo. You can see that when painter is drawing on qimage, some gray edges will appear, resulting in inconsistent effect with expectation. The main code is contained in paintwidget.cpp .