matchTemplate

[dominikdolancic]

I tried to write an example for matchTemplate but without success. Please if someone could write some example for using this function.
Thanks in advance,
Dominik

[dominikdolancic]

Error what i received is
OpenCV Error: Assertion failed ((img.depth() == CV_8U || img.depth() == CV_32F) && img.type() == templ.type()) in matchTemplate, file /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp, line 249
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp:249: error: (-215) (img.depth() == CV_8U || img.depth() == CV_32F) && img.type() == templ.type() in function matchTemplate

[salmanulhaq]

@padom template's Mat and the input image should both be of same type (single channel etc) and depth (8bit etc). Make sure that's the case.

[dominikdolancic]

They both are the same type and depth, template image is actually cropped copy of original. Do you have another idea?

[salmanulhaq]

are they RGB or single channel? You need to convert both template and input to single channel before running matchTemplate()

[dominikdolancic]

Thanks for helping, now I got another error.
I don't know where am I mistaken, my code looks like

Assertion failed: (object->InternalFieldCount() > 0), function Unwrap, file ../node_modules/nan/nan_object_wrap.h, line 33.
Abort trap: 6

cv.readImage("./test.jpg", function(err, im) {

              cv.readImage("./template.jpg", function(err, template) {

                var width = im.width();
                var height = im.height();
                if (width < 1 || height < 1) throw new Error('Image has no size');

                im.convertGrayscale();
                template.convertGrayscale();

                // Create the result matrix
                var result_cols = im.col() - template.col() + 1;
                var result_rows = im.row() - template.row() + 1;
                var result = new cv.Matrix(result_cols, result_rows, cv.Constants.CV_32FC1);

                im.matchTemplate(template, result, 3);

                result.save('./pic.jpg');

              });

 });

[salmanulhaq]

whats the exact error?

[bobvanluijt]

As a sidenote, I'm looking for the documentation on matchTemplate() where can I find this or should I go through the code?

[dominikdolancic]

I've just edited post above, here is the error

OpenCV Error: Assertion failed (corrsize.height <= img.rows + templ.rows - 1 && corrsize.width <= img.cols + templ.cols - 1) in crossCorr, file /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp, line 70
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp:70: error: (-215) corrsize.height <= img.rows + templ.rows - 1 && corrsize.width <= img.cols + templ.cols - 1 in function crossCorr

[salmanulhaq]

I just looked at the code to see what might be wrong. Here's your amended code which may work (I didn't test):

cv.readImage("./test.jpg", function(err, im) {
    im.convertGrayscale();
    im.matchTemplate("./template.jpg", 3, function(result){
        result.save('./pic.jpg');
    });
});

[dominikdolancic]

Doesn't work, same error like before

OpenCV Error: Assertion failed ((img.depth() == CV_8U || img.depth() == CV_32F) && img.type() == templ.type()) in matchTemplate, file /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp, line 249
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /tmp/opencv20160107-54198-1duzac3/opencv-2.4.12/modules/imgproc/src/templmatch.cpp:249: error: (-215) (img.depth() == CV_8U || img.depth() == CV_32F) && img.type() == templ.type() in function matchTemplate

[salmanulhaq]

there's an inherent issue which the author of this function may have overlooked. He reads the template image as:

cv::imread(filename, CV_8S);

which means he's reading it as 8bit signed image while it should've been 8U and not 8S. I can create a pull request with the fix though.

P.S: also just checked and OpenCV's matchTemplate doesn't require image to be single channel anymore.

[bobvanluijt]

@salmanulhaq does this mean we can't use the function at all or is there a workaround? I also did find this: http://stackoverflow.com/a/35727588/1501285

[dominikdolancic]

@salmanulhaq would be great if you could make the fix