将图像大小调整为正方形，但保持纵横比c ++ opencv

问题描述

有没有办法调整任何形状或大小的图像来说明 [500x500] 但是要保持图像的纵横比，使空白空间充满白色/黑色填充物？

Is there a way of resizing images of any shape or size to say [500x500] but have the image's aspect ratio be maintained, levaing the empty space be filled with white/black filler?

所以说图像是 [2000x1000] ，在调整大小到 [500x500] 使实际图像本身为 [500x250] ， 125 任何一面都是白色/黑色填充物。

So say the image is [2000x1000], after getting resized to [500x500] making the actual image itself would be [500x250], with 125 either side being white/black filler.

这样的事情：

输入

输出

编辑

我不希望简单在方形窗口中显示图像，而不是将图像更改为该状态，然后保存到文件中，创建尽可能少的图像失真的相同尺寸图像的集合。

I don't wish to simply display the image in a square window, rather have the image changed to that state and then saved to file creating a collection of same size images with as little image distortion as possible.

我遇到的唯一一个问类似问题的是，但它在 php 中。

The only thing I came across asking a similar question was this post, but its in php.

推荐答案

未完全优化，但你可以试试这个：

Not fully optimized, but you can try this:

编辑处理目标大小不是 500x500 像素并将其作为一个函数包装起来。

EDIT handle target size that is not 500x500 pixels and wrapping it up as a function.

cv::Mat GetSquareImage( const cv::Mat& img, int target_width = 500 )
{
    int width = img.cols,
       height = img.rows;

    cv::Mat square = cv::Mat::zeros( target_width, target_width, img.type() );

    int max_dim = ( width >= height ) ? width : height;
    float scale = ( ( float ) target_width ) / max_dim;
    cv::Rect roi;
    if ( width >= height )
    {
        roi.width = target_width;
        roi.x = 0;
        roi.height = height * scale;
        roi.y = ( target_width - roi.height ) / 2;
    }
    else
    {
        roi.y = 0;
        roi.height = target_width;
        roi.width = width * scale;
        roi.x = ( target_width - roi.width ) / 2;
    }

    cv::resize( img, square( roi ), roi.size() );

    return square;
}

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