FishEye Picture Effect (Barrel Distortion) Algorithm (with Java)?

Question

I am looking for an algorithm (bitmap pixel manipulation) to simulate a Barrel Distortion from ordinary images. So far I have found an implementation involving external libraries such as OpenCV, OpenGL or jhlabs. Since I am doing a class in the field of digital image processing and I am doing a course assessment project, I am not sure that using any external library will bring me a good grade. So will someone give me a link to such an algorithm?

Ps. I will be asked to implement it in Java, but an example from any language will do.

Answer 1

, , , . - , , , , . , .

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, OpenCV . , cv:

$ grep -o "cv\\w*" barrel.cpp | sort | uniq
cv
cvCreateImage
cvGet2D
cvGetSize
cvLoadImage
cvNamedWindow
cvSaveImage
cvSet2D
cvShowImage
cvWaitKey

API OpenCV, , , , , .. . , OpenCV.

, :

float getRadialX(float x,float y,float cx,float cy,float k){
  x = (x*xscale+xshift);
  y = (y*yscale+yshift);
  float res = x+((x-cx)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy)));
  return res;
}

float getRadialY(float x,float y,float cx,float cy,float k){
  x = (x*xscale+xshift);
  y = (y*yscale+yshift);
  float res = y+((y-cy)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy)));
  return res;
}

- , . , OpenCV.

Answer 2

http://www.helviojunior.com.br/fotografia/barrel-and-pincushion-distortion/

Answer 3

https://android.googlesource.com/platform/frameworks/base/+/ac39c604d6df8631922c2295b3341cd561f172a5/media/mca/filterpacks/java/android/filterpacks/imageproc/FisheyeFilter.java

it should be what you want.

look at the shader mFishEyeShaderandupdateProgramParams()