本文主要是介绍使用opencv将Mat图像resize成检测输入的letterbox类型，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
1.python代码
a.resize def my_letter_box(img, size=(640, 640)): #h, w, c = img.shaper = min(size[0] / h, size[1] / w)new_h, new_w = int(h * r), int(w * r)top = int((size[0] - new_h) / 2)left = int((size[1] - new_w) / 2)bottom = size[0] - new_h - topright = size[1] - new_w - leftimg_resize = cv2.resize(img, (new_w, new_h))img = cv2.copyMakeBorder(img_resize, top, bottom, left, right, borderType=cv2.BORDER_CONSTANT,value=(114, 114, 114))return img, r, left, top
b.返回原图坐标
def restore_box(boxes, r, left, top): # 返回原图上面的坐标boxes[:, [0, 2]] -= leftboxes[:, [1, 3]] -= topboxes[:, [0, 2]] /= rboxes[:, [1, 3]] /= rreturn boxes
2.c++代码
a.resize
float get_input_data_letterbox(cv::Mat mat, cv::Mat& img_new, int letterbox_rows, int letterbox_cols, int& left,int&top,bool bgr2rgb = false)
{
/* letterbox process to support different letterbox size */
if (!mat.data || letterbox_rows<1 || letterbox_cols<1)
return 1.0;
float scale_letterbox;
int resize_rows;
int resize_cols;
if ((letterbox_rows * 1.0 / mat.rows) < (letterbox_cols * 1.0 / mat.cols))
{
scale_letterbox = (float)letterbox_rows * 1.0f / (float)mat.rows;
}
else
{
scale_letterbox = (float)letterbox_cols * 1.0f / (float)mat.cols;
}
resize_cols = int(scale_letterbox * (float)mat.cols);
resize_rows = int(scale_letterbox * (float)mat.rows);
//cv::Mat img_new(letterbox_rows, letterbox_cols, CV_8UC3);
cv::resize(mat, mat, cv::Size(resize_cols, resize_rows));
top = (letterbox_rows - resize_rows) / 2;
int bot = (letterbox_rows - resize_rows + 1) / 2;
left = (letterbox_cols - resize_cols) / 2;
int right = (letterbox_cols - resize_cols + 1) / 2;
// Letterbox filling
cv::copyMakeBorder(mat, img_new, top, bot, left, right, cv::BORDER_CONSTANT, cv::Scalar(128, 128, 128));
if (bgr2rgb)
{
cv::cvtColor(img_new, img_new, cv::COLOR_BGR2RGB);
}
return scale_letterbox;
}
b.返回原图坐标
x0 = (x0 - left) /scale_letterbox;
y0 = (y0 - top) /scale_letterbox;
x1 = (x1 - left) /scale_letterbox;
y1 = (y1 - top) /scale_letterbox;
x0 = std::max(std::min(x0, (float)(src_cols - 1)), 0.f);
y0 = std::max(std::min(y0, (float)(src_rows - 1)), 0.f);
x1 = std::max(std::min(x1, (float)(src_cols - 1)), 0.f);
y1 = std::max(std::min(y1, (float)(src_rows - 1)), 0.f);
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