Pete`s Messageboard Forum - OGL2 shaders - Pixel preserving scalers

I think this might be a great idea since point and linear samplers (in general) give a blurry/distorted results. This can be compensated by using an alternative interpolation method. The end image can look like linear or point interpolated - or anything in between.
In the shader posted below this can be managed by the *p* value (p like power of...).

p = 1.0 - linear interpolation
p = 10.0 - almost point interpolation.

Code (2xSaL smart - is a fine example):

vertex shader:

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/*

2xSaL Smart shader (pow-metric)

- Copyright (C) 2007 guest(r) - guest.r@gmail.com

- License: GNU-GPL
*/



uniform sampler2D OGL2Texture;

const float p = 1.5; // value to be played with

const vec3 dt = vec3(1.0,1.0,1.0);

vec3 mux (vec3 a, vec3 b, float x, float p)
{
float xa = pow(x,p);
float xb = pow(1-x,p);
return (axa + bxb)/(xa+xb);
}


void main()
{

// Calculating texel coordinates

vec2 size = vec2(2048.0,1024.0);
vec2 inv_size = vec2(1.0/2048.0, 1.0/1024.0);

vec2 OGL2Pos = gl_TexCoord[0].xy*size;
vec2 fp = fract(OGL2Pos);
vec2 dx = vec2(inv_size.x,0.0);
vec2 dy = vec2(0.0,inv_size.y);
vec2 g1 = vec2( inv_size.x,inv_size.y);
vec2 g2 = vec2(-inv_size.x,inv_size.y);

vec2 pC4 = floor(OGL2Pos)*inv_size;


// Reading the texels

vec3 C0 = texture2D(OGL2Texture,pC4-g1).xyz;
vec3 C1 = texture2D(OGL2Texture,pC4-dy).xyz;
vec3 C2 = texture2D(OGL2Texture,pC4-g2).xyz;
vec3 C3 = texture2D(OGL2Texture,pC4-dx).xyz;
vec3 C4 = texture2D(OGL2Texture,pC4 ).xyz;
vec3 C5 = texture2D(OGL2Texture,pC4+dx).xyz;
vec3 C6 = texture2D(OGL2Texture,pC4+g2).xyz;
vec3 C7 = texture2D(OGL2Texture,pC4+dy).xyz;
vec3 C8 = texture2D(OGL2Texture,pC4+g1).xyz;

vec3 ul,ur,dl,dr; float m1,m2;

m1=dot(abs(C0-C4),dt)+0.001;
m2=dot(abs(C1-C3),dt)+0.001;
ul=(m2(C0+C4)+m1(C1+C3))/(m1+m2);

m1=dot(abs(C1-C5),dt)+0.001;
m2=dot(abs(C2-C4),dt)+0.001;
ur=(m2(C1+C5)+m1(C2+C4))/(m1+m2);

m1=dot(abs(C3-C7),dt)+0.001;
m2=dot(abs(C6-C4),dt)+0.001;
dl=(m2(C3+C7)+m1(C6+C4))/(m1+m2);

m1=dot(abs(C4-C8),dt)+0.001;
m2=dot(abs(C5-C7),dt)+0.001;
dr=(m2(C4+C8)+m1(C5+C7))/(m1+m2);

gl_FragColor.xyz = 0.5*(mux(mux(dr,dl,fp.x,p),mux(ur,ul,fp.x,p),fp.y,p));
}

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Pixel preserving scalers

Pixel preserving scalers