Image Warping - Bulge Effect Algorithm

image algorithm image-processing

12,806

Solution 1

See if I understood what you want. Suppose your image coordinates go from 0 to 1.

If you do:

r = Sqrt[(x - .5)^2 + (y - .5)^2]
a = ArcTan[x - .5, y - .5]
rn = r^2.5/.5

And then remap your pixels according to:

  x -> rn*Cos[a] + .5 
  y -> rn*Sin[a] + .5

You get:

You may adjust the parameters to get bigger or smaller bulges.

Edit

Let's see if I understood your comment about warping. The following images are generated using

rn = r^k {k: 1 ... 2}:

Solution 2

GLSL code version:

uniform sampler2D tex;

void main()
{
 vec2 cen = vec2(0.5,0.5) - gl_TexCoord[0].xy;
 vec2 mcen = - // delete minus for implosion effect
      0.07*log(length(cen))*normalize(cen);
 gl_FragColor = texture2D(tex, gl_TexCoord[0].xy+mcen);
}

original:

enter image description here

explosion:

enter image description here

implosion:

enter image description here

cheers!

12,806

random

Updated on October 21, 2020

Comments

random over 3 years

Can any point to image warping algorithms? Specifically for bulge effect?
- YoungDev over 2 years
  
  May you help me with this? stackoverflow.com/questions/70683954/how-can-i-do-image-warp
sedavidw over 13 years

You don't really need to go into trigonometry. Cos[a] = (x - .5)/r and Sin[a] = (y - .5)/r
random over 13 years

Check the algorithm in this link - davis.wpi.edu/~matt/courses/morph/2d.htm Can we have an algorithm like this for bulge effect?
random over 13 years

Thanks belisarius. I now need to implement it by adding a mesh to a Sprite in Android and applying the deformation to it. We have a library called andEngine which we can utilize. I have created another thread to proceed further: stackoverflow.com/questions/5078240/…
Dr. belisarius over 13 years

@user193545 Can't help you wih that one. Good luck!
BlueRaja - Danny Pflughoeft about 13 years

See also my followup to this answer here
arunkumar.p almost 13 years

Can you explain as briefly with any example
Vivek Kumar Srivastava almost 13 years

I am unable to get above effect by using your alogorithm.
Ajay Sharma over 12 years

@belisarius Can you help me with detecting the Objects shape witin an image ?
Dr. belisarius over 12 years

@Ajay May be. Post a question and ping me again :)
CCJ over 11 years

@belisarius I'm interested in garnering a deeper understanding of the math involved in the image warp you describe above; I've opened a thread over at math.stackexchange.com to that end: math.stackexchange.com/questions/266250/… I'd really appreciate your input! Thanks very much!
AAnkit over 11 years

how to use it in Android with bitmap?