《Fast Approximate Anti-Aliasing (FXAA) (GLSL)》

[Vertex_Shader] 
varying vec4 posPos; 
uniform float FXAA_SUBPIX_SHIFT = 1.0/4.0; 
uniform float rt_w; // GeeXLab built-in 
uniform float rt_h; // GeeXLab built-in 

void main(void) 
{ 
    gl_Position = ftransform();
    gl_TexCoord[0] = gl_MultiTexCoord0; 
    vec2 rcpFrame = vec2(1.0/rt_w, 1.0/rt_h); 
    posPos.xy = gl_MultiTexCoord0.xy; 
    posPos.zw = gl_MultiTexCoord0.xy - (rcpFrame * (0.5 + FXAA_SUBPIX_SHIFT)); 
}

[Pixel_Shader]
#version 120 
uniform sampler2D tex0; // 0 
uniform float vx_offset; 
uniform float rt_w; // GeeXLab built-in 
uniform float rt_h; // GeeXLab built-in 
uniform float FXAA_SPAN_MAX = 8.0; 
uniform float FXAA_REDUCE_MUL = 1.0/8.0; 
varying vec4 posPos; 
#define FxaaInt2 ivec2 
#define FxaaFloat2 vec2 
#define FxaaTexLod0(t, p) texture2DLod(t, p, 0.0) 
#define FxaaTexOff(t, p, o, r) texture2DLodOffset(t, p, 0.0, o) 

vec3 FxaaPixelShader
        ( vec4 posPos, // Output of FxaaVertexShader interpolated across screen.
          sampler2D tex, // Input texture. 
          vec2 rcpFrame) // Constant {1.0/frameWidth, 1.0/frameHeight}.
{

    #define FXAA_REDUCE_MIN (1.0/128.0) 
    //#define FXAA_REDUCE_MUL (1.0/8.0) 
    //#define FXAA_SPAN_MAX 8.0 
    vec3 rgbNW = FxaaTexLod0(tex, posPos.zw).xyz; 
    vec3 rgbNE = FxaaTexOff(tex, posPos.zw, FxaaInt2(1,0), rcpFrame.xy).xyz; 
    vec3 rgbSW = FxaaTexOff(tex, posPos.zw, FxaaInt2(0,1), rcpFrame.xy).xyz; 
    vec3 rgbSE = FxaaTexOff(tex, posPos.zw, FxaaInt2(1,1), rcpFrame.xy).xyz; 
    vec3 rgbM = FxaaTexLod0(tex, posPos.xy).xyz; 
    vec3 luma = vec3(0.299, 0.587, 0.114); 
    float lumaNW = dot(rgbNW, luma); 
    float lumaNE = dot(rgbNE, luma); 
    float lumaSW = dot(rgbSW, luma); 
    float lumaSE = dot(rgbSE, luma); 
    float lumaM = dot(rgbM, luma); 
    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE))); 
    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE))); 
    vec2 dir; 
    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE)); 
    dir.y = ((lumaNW + lumaSW) - (lumaNE + lumaSE)); 
    float dirReduce = max( (lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 *FXAA_REDUCE_MUL), FXAA_REDUCE_MIN); 
    float rcpDirMin = 1.0/(min(abs(dir.x), abs(dir.y)) + dirReduce); 
    dir = min(FxaaFloat2( FXAA_SPAN_MAX, FXAA_SPAN_MAX),     max(FxaaFloat2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX), dir * rcpDirMin)) * rcpFrame.xy; 
    vec3 rgbA = (1.0/2.0) * ( FxaaTexLod0(tex, posPos.xy + dir * (1.0/3.0 - 0.5)).xyz + FxaaTexLod0(tex, posPos.xy + dir * (2.0/3.0 - 0.5)).xyz); 
    vec3 rgbB = rgbA * (1.0/2.0) + (1.0/4.0) * ( FxaaTexLod0(tex, posPos.xy + dir * (0.0/3.0 - 0.5)).xyz + FxaaTexLod0(tex, posPos.xy + dir * (3.0/3.0 - 0.5)).xyz); 
    float lumaB = dot(rgbB, luma); 
    if((lumaB < lumaMin) || (lumaB > lumaMax)) 
        return rgbA; 
    return rgbB; 
}

vec4 PostFX(sampler2D tex, vec2 uv, float time) 
{ 
    vec4 c = vec4(0.0); 
    vec2 rcpFrame = vec2(1.0/rt_w, 1.0/rt_h); 
    c.rgb = FxaaPixelShader(posPos, tex, rcpFrame); 
    //c.rgb = 1.0 - texture2D(tex, posPos.xy).rgb; 
    c.a = 1.0; 
    return c; 
} 

void main() 
{
    vec2 uv = gl_TexCoord[0].st; 
    gl_FragColor = PostFX(tex0, uv, 0.0); 
}

note:
set FXAA_REDUCE_MUL and FXAA_SUBPIX_SHIFT to 0.0 by default to get the finest rendering.