To frame = cv2.resize(frame, None, fx=0.5, fy=0.5) I changed my code from frame = cv2.resize(frame, (0,0), fx=0.5, fy=0.5) I am having OpenCV version 3.4.3 on MacOS. Weirdly, by removing the spaces the function worked just fine. I know this is a very old thread but I had the same problem which was due spaces in the images names. astype('uint8') resolved the issue for me. Img = cv2.resize(img, (width, height), interpolation = cv2.INTER_AREA)Īlso pay attention to the object type of your numpy array, converting it using. """Function to return an image with the size I want""" Now I have an extra step before attempting the resize operation, which is to do the assertion myself: def getSizedFrame(width, height): Turns out for me this error was actually telling the truth - I was trying to resize a Null image, which was usually the 'last' frame of a video file, so the assertion was valid. For images with height larger than width, it's the following line that causes error: CV_Assert( dsize.area() > 0 ) While not ideal, it works for me.Īnd I just recently found out that the above applies only to image whose width is larger than height. A temporary fix is to build OpenCV with this line commented out. This appears to be a bug in OpenCV and hopefully will be fixed in the future release. When the product of rows and columns of the image to be resized is larger than 2^31, ssize.area() results in a negative number. The output size format is (width, height)Ģ.So it turns out that the problem comes from one line in modules\imgproc\src\imgwarp.cpp: CV_Assert( ssize.area() > 0 ) INTER_LANCZOS4 Lanczos interpolation of 8x8 pixel neighborhoodġ. INTER_CUBIC 4x4 pixel neighborhood bicubic interpolation INTER_AREA uses pixel area relations for resampling. INTER_LINEAR Bilinear interpolation (default setting) INTER_NEAREST nearest neighbor interpolation Interpolation using the interpolation method options: Image scaling of Python-OpenCV (cv2.resize)Ĭv2.resize(InputArray src, OutputArray dst, Size, fx, fy, interpolation)įx, fy along the x-axis, y-axis scale factor Resize(src, dst, dst.size(), 0, 0, interpolation) But if you have specified the size of the dst image in advance, then you can call the function in the following way: The type is inherited from the src image, and the size is also calculated from the original image according to the parameters. Under normal circumstances, the size and type of the dst image are not known before use. The efficiency of several commonly used methods is: nearest neighbor interpolation>bilinear interpolation>bicubic interpolation>Lanczos interpolation īut efficiency and effect are inversely proportional, so use it according to your own situation.ģ. As for the final interpolation method, the default bilinear interpolation is sufficient under normal circumstances. Or you can let dsize be 0 and specify the values of fx and fy, such as fx=fy=0.5, then it is equivalent to doubling the original image in both directions!Ģ. dsize and fx/fy cannot be 0 at the same time, or you can specify the value of dsize so that fx and fy are vacant and use the default value directly, like resize(img, img2, Size(20, 20)) //resize to any size, 20*20ĬvResize is often used in IplImage operations, and resize is often used in Mat operations.ġ. resize(img,img2,Size(img.cols*scale,img.rows*scale)) //reduced to 1/2 Size dsize = Size(img.cols*scale, img.rows*scale) Note: dsize and (fx, fy) cannot be 0 at the same time Similarly, interpolation is also the corresponding modification and interpolation method, including nearest neighbor, bilinear, Bi-cubic, based on the pixel area relationship, and Lanzos interpolation methods, because I haven't used them before, I generally use the default, the principle is not clear. When zooming in the image, it is similar to the method CV_INTER_NN.ĬV_EXPORTS_W void resize( InputArray src, OutputArray dst, Size dsize, double fx=0, double fy=0, When shrinking the image, this method can avoid the appearance of moire. CV_INTER_AREA-pixel area related resampling.CV_INTER_LINEAR-double line Interpolation (default method). ![]() ♼V_INTER_NN-nearest neighbor interpolation ![]() Where interpolation is the method of modification and interpolation, and the values are as follows: cvResize: Function prototypeĬVAPI(void) cvResize( const CvArr* src, CvArr* dst, int interpolation CV_DEFAULT( CV_INTER_LINEAR )) ![]() Opencv provides two functions cvResize() and resize() for corresponding zooming operations When implementing image window display, it often appears that the image is too large or too small to effectively display the full image.
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