问题描述
以下是我对图像进行预处理的尝试.这涉及以下步骤
The following is my attempt to preprocess an image. That involves the followings steps
- 戴上口罩
- 收获结果
- 最后,将像素值缩放为255
当我尝试从第3步返回到第2步时,我得到的是黑白图像,而不是灰度图像.以下是我执行预处理的代码
When I try to go back from step 3 to step 2, I get a black and white image instead of a grayscale one.The following is my code to perform preprocessing
cv::Mat maskCrop(std::string imageName, std::string maskName)
{
cv::Mat image,mask;
image = cv::imread( imageName, CV_LOAD_IMAGE_GRAYSCALE);
mask = cv::imread( maskName,CV_LOAD_IMAGE_GRAYSCALE);
cv::Mat final_image;
cv::resize(image, image, mask.size()); // make the size of mask and image same
cv::bitwise_and(image, mask, final_image); //Apply mask
// define rectangular window for cropping
int offset_x = 1250; // top left corner, for cropping
int offset_y = 1550;
cv::Rect roi;
roi.x = offset_x;
roi.y = offset_y;
roi.width = 550;
roi.height = 650;
// Crop the original image to the defined ROI //
cv::Mat crop = final_image(roi);
//scale the image
float beta = 1.0 / 255.0;
crop *=beta; // divide the max pixel vaue i.e. 255
//Examinig whether scaling can be undone !!!!
cv::imwrite("/home/dpk/Desktop/ip-rings/gray_image.jpg",crop*255);
return crop;
}
以下是当我尝试按255撤消缩放比例时获得的输出(第3步)
The following is the output that I get when I try to undo scaling by 255(step 3)
以下是预期的输出
什么导致图像为黑白而不是灰度?
What causes the image to be black and white instead of grayscale?
推荐答案
这是因为数据类...我认为crop
矩阵类是uchar
,当您除以255时,输出为0或1 (介于0到254之间的每个强度为零,而255为1),当您在255中乘以输出时,输出将为0和255.所以测试这段代码
It's because class of data... I assume that the crop
matrix class is uchar
and when you divide to 255 the output is 0 or 1 (every intensity between 0 to 254 is zero and 255 will be 1) and when you multipy output in 255 the output will be 0 and 255.so test this code
{
.
.
cv::Mat crop = final_image(roi);
crop.convertTo(crop,
CV_32F, //New Type
1.0f/255, //Scaling
0); //offset
cv::imwrite("/home/dpk/Desktop/ip-rings/gray_image.jpg",crop*255);
return crop;
}
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