crop image

crop

asked 2012-07-31 14:18:13 -0600

andrea
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updated 2012-07-31 14:18:29 -0600

hi!

someone know how to use crop for the image?

for example i have one image i want to show a part of this image...

i read that there are the cvRect and cvSetImageROI.....

thanks a lot :)

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answered 2012-07-31 14:30:18 -0600

Michael Burdinov
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Mat cropedImage = fullImage(Rect(roiX,roiY,roiWidth,roiHeight));

Also note that this operation doesn't really perform cropping or coping memory. croppedImage uses same memory buffer as fullImage, so any changes of one of them may affect another.

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thanks :)

andrea ( 2012-07-31 14:40:04 -0600 )edit

sorry have another question... but if i want to crop a region that is not a rect? for example i have 4 point (the vertices) and i want the region delimited by this vertices (almost of the time is a rectangle but not always)

andrea ( 2012-07-31 14:44:35 -0600 )edit

You should crop the bounding rectangle in the same way as Michael suggested. But then you can call cv:fillPoly (http://docs.opencv.org/modules/core/doc/drawing_functions.html?highlight=poly#cv.FillPoly) to create a mask for your region. You can keep the mask in a separate matrix, or add to the submatrix as an alpha channel (4th channel in the CV_8UC4 matrix).