作者：徐景周
在放大或缩小图像时，如何能最好的保持图像原态比例来显示呢？下面提供一个涵数可帮你来实现，调用它后，返回的矩形区域既为最佳显示图像大小。
l 涵数中的第一个参数rcScreen为图像要被显示的矩形大小，第二个参数sizePicture为图像自身大小，第三个参数bCenter为是否居中显示，返回值CRect既为图像最佳显示大小。
涵数如下所示：
CRect RectSizeWithConstantRatio( CRect* rcScreen, CSize sizePicture, BOOL bCenter) { CRect rect(rcScreen); double dWidth = rcScreen->Width(); double dHeight = rcScreen->Height(); double dAspectRatio = dWidth/dHeight; double dPictureWidth = sizePicture.cx; double dPictureHeight = sizePicture.cy; double dPictureAspectRatio = dPictureWidth/dPictureHeight; //If the aspect ratios are the same then the screen rectangle // will do, otherwise we need to calculate the new rectangle if (dPictureAspectRatio > dAspectRatio) { int nNewHeight = (int)(dWidth/dPictureWidth*dPictureHeight); int nCenteringFactor = (rcScreen->Height() - nNewHeight) / 2; rect.SetRect( 0, nCenteringFactor, (int)dWidth, nNewHeight + nCenteringFactor); } else if (dPictureAspectRatio < dAspectRatio) { int nNewWidth = (int)(dHeight/dPictureHeight*dPictureWidth); int nCenteringFactor = (rcScreen->Width() - nNewWidth) / 2; rect.SetRect( nCenteringFactor, 0, nNewWidth + nCenteringFactor, (int)(dHeight)); } return rect; };
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