Explosion and implosion Pixel Shader

Explosion/Implosion filter can be modeled by shifting pixel outwards/towards the center of image by value which is proportional to pixel distance from the center of image.
Explosion/Implosion pixel shader code in GLSL:

---

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);
}

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By applying this filter to image below

we get such explosion effect

and such implosion effect