I want to cut a renctangular shape out of an image.
I know the position of the rectangle relative to the orginal image.
However: When I rotate/scale/translate the image, the image dimensions changes. So my crop to the rectangle does not work anymore.
Is there a way to preserve the "old" coordinate system while transforming the image and then do a crop based on that old system?
The Image is always rotated/scaled around its center. Translation is applied after scaling and rotation.
I aim for a solution in php with imagick. However: When its not possible I am fine with command line imagemagick, too
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I have two images, one that is a monochrome one which is a mask and another one with full color. What I need to do is find the CGRect of the mask (white pixels) in the other full color one.
What I did is to first find the contour of the mask using the Vision framework. Now, this returns a CGPath which is normalised. How can I translate this path into coordinates to the other image? Both have been scaled the same way to make them the same size so the translation should be "easy" but I can't figure it out.
I have an random shape bitmap cut out by user. I want to fade out its borders i.e. contours, so as to make it appear smooth. What should I do? To get the borders and color of every pixel in bitmap, I am traversing it pixel by pixel. It takes long time, still I am ok with it. Is openCV my only option? If yes, can anybody point me towards any tutorial or suggestion for logical approach?
You can just run a smoothing filter on your shape.
In opencv you can use the blur fnnction or gaussainBlur. Look at http://docs.opencv.org/2.4/doc/tutorials/imgproc/gausian_median_blur_bilateral_filter/gausian_median_blur_bilateral_filter.html.
You don't have to use opencv but i think it would be easier and faster.
If you still don't want can use any other code that implement smoothing an image.
In case you just want to effect the border pixels do the following:
Make a copy of the original image
Filter the entire image.
Extract the border pixel using opencv findContours.
Copy from the blurred image only the pixels in the border and in there neighborhood and copy them to the copy you did in step 1.
I am trying to crop a picture on right on along the contour. The object is detected using surf features and than i want to crop the image of extactly as detected.
When using crop some outside boundaries of other object is includes. I want to crop along the green line below. OpenCV has RotatedRect but i am unsure if its good for cropping.
Is there way to perfectly crop along the green line
I assume you get you get your example from http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html, so what you can do is to find the minimum axis aligned bounding box around the green bounding box, crop it from the image, use the inverted homography (H.inv()) matrix to transform that sub image into a new image (call cv::warpPerspective), and then crop your green bounding box (it should be axis aligned in your new image).
You can get the equations of the lines from the end points for each. Use these equations to check whether any given pixel lies within the green box or not i.e. does it lie between the left and right lines and between the top and bottom lines. Run this over the entire image and reset anything that doesn't lie within the box to black.
Not sure about in-built functionality to do this, but this simple methodology is guaranteed to work. For higher accuracy, you may want to consider sub-pixel checks.
I am trying to make double chin in fat image as mentioned in my desired result image below.
I have morphed the normal face to fat face by wrapping an image on mesh and deformed the mesh.
Original image
Wrapped image on mesh grid with vertex points displaced
Current result image
I tried a lot by arranging mesh points but could not get the result like I have shown in first image.
Any ideas how to achieve this by open GL or open CV in iOS?
It's obvious from the first image that there is an added effect to produce the double or triple chin.
This actually looks like a either a preset image blended into the original or a scale and stretched version of the original chin blended into the warped image.
The application PhotoFiltre has an option to stretch part of an image. You select a rectangular shape and you can then grab and move the vertexes somewhere else to make any quadrangle. The image part which you selected will stretch along. Hopefully these images make my point a little clearer:
Is there a general algorithm which can handle this? I would like to obtain the same effect on HTML5 canvas - given an image and the resulting corner points, I would like to be able to draw the stretched image in such a way that it fills the new quadrangle neatly.
A while ago I asked something similar, where the solution was to divide the image up in triangles and stretch each triangle so that each three points correspond to the three points on the original image. This technique turned out to be rather exprensive and I would like if there is a more general method of accomplishing this.
I would like to use this in a 3D renderer, but I would like to work with a (2D) quadrangle.
I don't know whether PhotoFiltre internally also uses triangles, or whether it uses another (cheaper) algorithm to stretch an image like this.
Does someone perhaps know if there is a cheaper or more general method/algorithm to stretch a rectangular image, so that it fills a quadrangle given four points?
The normal method is to start with the destination, pick an appropriate grid size and then for each point in the new shape calculate the corresponding point in the source image (possibly with interpolation depending on the quality you need)
Affine transform.
Given four points for the "stretched" figure and four points for the figure it should match (e.g. a rectangle), an affine transform provides the spatial mapping you need. For each point (x1,y1) in the original image there is a corresponding point (x2,y2) in the second, "stretched" image.
For each integer-valued pixel (x2, y2) in the stretched image, use the affine transform to find the corresponding real-valued point (x1, y1) in the original image and apply its color to (x2,y2).
http://demonstrations.wolfram.com/AffineTransform/
You'll find sample code for Java and other languages online. .NET has the Matrix class.