效果图

指数5
指数15

指数40

原理

马赛克的原理很简单，就是取一个值，让这个值作为一个方格子的长宽，如40*40px的格子，取这个区域的平均R G B值，然后这个区域的所有像素点都是这个RGB值即可

源码

QImage applyMosaic(const QImage& oldImage, int blockSize) {
    if (oldImage.isNull() || blockSize <= 0) {
        return QImage(); // 返回空图片或处理错误
    }

    // 确保blockSize是偶数，并且不会使图像尺寸变得太小
    blockSize = (blockSize % 2 == 0) ? blockSize : blockSize + 1;
    if (oldImage.width() < blockSize || oldImage.height() < blockSize) {
        return oldImage; // 如果blockSize太大，直接返回原图
    }

    // 计算新图片的尺寸
    int newWidth = oldImage.width() / blockSize * blockSize;
    int newHeight = oldImage.height() / blockSize * blockSize;

    QImage newImage(newWidth, newHeight, oldImage.format());

    // 遍历每个块
    for (int y = 0; y < newHeight; y += blockSize) {
        for (int x = 0; x < newWidth; x += blockSize) {
            // 计算块的平均颜色
            QRgb averageColor = qRgb(0, 0, 0); // 初始化平均颜色为黑色
            int totalR = 0, totalG = 0, totalB = 0;
            int count = 0;

            for (int by = 0; by < blockSize && y + by < oldImage.height(); ++by) {
                for (int bx = 0; bx < blockSize && x + bx < oldImage.width(); ++bx) {
                    QRgb pixel = oldImage.pixel(x + bx, y + by);
                    totalR += qRed(pixel);
                    totalG += qGreen(pixel);
                    totalB += qBlue(pixel);
                    ++count;
                }
            }

            if (count > 0) { // 确保count不是0，避免除以0
                averageColor = qRgb(totalR / count, totalG / count, totalB / count);
            }

            // 用平均颜色填充整个块
            for (int by = 0; by < blockSize && y + by < newImage.height(); ++by) {
                for (int bx = 0; bx < blockSize && x + bx < newImage.width(); ++bx) {
                    newImage.setPixel(x + bx, y + by, averageColor);
                }
            }
        }
    }

    return newImage;
}