将 QImage 转换为灰度

Convert a QImage to grayscale(将 QImage 转换为灰度)

问题描述

我有一个 QImage，我需要将它转换为灰度，然后再用颜色绘制它.我发现了一个 allGray() 和 isGrayScale() 函数来检查图像是否已经是灰度的，但没有 toGrayScale() 或类似名称功能.

I have a QImage and I need to convert it to grayscale, then later paint over that with colors. I found an allGray() and isGrayScale() function to check if an image is already grayscale, but no toGrayScale() or similarly-named function.

现在我正在使用这段代码，但它的性能不是很好:

Right now I'm using this code, but it's does not have a very good performance:

for (int ii = 0; ii < image.width(); ii++) {
    for (int jj = 0; jj < image.height(); jj++) {
        int gray = qGray(image.pixel(ii, jj));
        image.setPixel(ii, jj, QColor(gray, gray, gray).rgb());
    }
}

在性能方面，将 QImage 转换为灰度的最佳方法是什么?

What would be the best way, performance-wise, to convert a QImage to grayscale?

推荐答案

从 Qt 5.5 开始，您可以调用 QImage::convertToFormat() 将 QImage 转换为灰度，如下所示:

Since Qt 5.5, you can call QImage::convertToFormat() to convert a QImage to grayscale as follows:

QImage image = ...;
image.convertToFormat(QImage::Format_Grayscale8);

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