[英]OpenCV Mat::data is zero after image operation
I have a problem in OpenCV C++. 我在OpenCV C ++中有问题。 I read in an image from file and use the threshold-function to get a binary image. 我从文件中读取图像,并使用阈值功能获取二进制图像。 After that I want to access the pixel values of the thresholded image. 之后,我要访问阈值图像的像素值。
PROBLEM: The Mat::data array of the thresholded image is 0. 问题:阈值图像的Mat :: data数组为0。
I use threshold(src, img, 220, 255, CV_THRESH_BINARY); 我使用阈值(src,img,220,255,CV_THRESH_BINARY); with src and img beig cv::Mat. 与src和img beig cv :: Mat。
After that call in the img::data = " " 之后,在img :: data =“”中调用
Here is my code: 这是我的代码:
// read image source
Mat src = imread("image.png", CV_LOAD_IMAGE_COLOR);
if(src.empty())
{
return -1;
}
cvtColor(src,src,CV_RGB2GRAY);
threshold(src, src, 220, 255, CV_THRESH_BINARY );
int line[1200];
int lineCount = 0;
for(int i=src.rows; i>src.rows/2; i-=10)
{
uchar* rowi = src.ptr(i-1);
int columnCount = 0;
// begin on the left of the image
for(int j=0; j<src.cols; j++)
{
uchar grayscale = src.at<uchar>(rowi[j]);
// write data to array
line[columnCount] = grayscale;
columnCount++;
}
}
I think the problem might be about cv::Mat with referencing and copying Mat::data: 我认为问题可能与引用和复制Mat :: data的cv :: Mat有关:
Thanks for your help! 谢谢你的帮助!
I suppose you have checked that your image.png (after having been converted to grayscale) contains values higher than 220? 我想您已经检查过image.png(转换为灰度后)包含的值大于220吗?
You may want to try to perform cvtColor
as a non-in-place operation, as it might not properly support in-place conversion (see https://stackoverflow.com/a/15345586/19254 ). 您可能想尝试将cvtColor
作为非就地操作执行,因为它可能无法正确支持就地转换(请参阅https://stackoverflow.com/a/15345586/19254 )。 This you would do for example like this: 例如,您可以这样做:
Mat dst;
cvtColor(src, dst, CV_RGB2GRAY);
... and then do threshold
on dst
. ...然后在dst
threshold
。 Alternatively, you could read the image into memory in grayscale mode to begin with (second parameter to imread
can be CV_LOAD_IMAGE_GRAYSCALE
), in which case the cvtColor
call is not necessary. 或者,您可以从灰度模式开始将图像读取到内存中(要imread
第二个参数可以是CV_LOAD_IMAGE_GRAYSCALE
),在这种情况下, cvtColor
调用。
Between each call, you can imwrite
your image to disk in order to find out which step is not working as expected. 每次调用之间,你可以imwrite
图像到磁盘,以找出哪些步骤无法按预期工作。
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