Help with Pixel Shader effect for brightness and contrast

What is a simple pixel shader script effect to apply brightness and contrast?

I found this one, but it doesn't seem to be correct:

sampler2D input : register(s0);
float brightness : register(c0);
float contrast : register(c1);

float4 main(float2 uv : TEXCOORD) : COLOR
{
    float4 color = tex2D(input, uv); 
    float4 result = color;
    result = color + brightness;
    result = result * (1.0+contrast)/1.0;

    return result;
}

thanks!

From stackoverflow

• That contrast calculation looks wrong to me. If you leave it out, does your brightness work ok?

• Is this what you are looking for?

  float Brightness : register(C0);
  float Contrast : register(C1);
  
  sampler2D Texture1Sampler : register(S0);
  
  float4 main(float2 uv : TEXCOORD) : COLOR
  {
  
     float4 pixelColor = tex2D(Texture1Sampler, uv);
     pixelColor.rgb /= pixelColor.a;
  
    // Apply contrast.
    pixelColor.rgb = ((pixelColor.rgb - 0.5f) * max(Contrast, 0)) + 0.5f;
  
    // Apply brightness.
    pixelColor.rgb += Brightness;
  
    // Return final pixel color.
    pixelColor.rgb *= pixelColor.a;
  
  
   return pixelColor;
  }
  

  --- Tested with Shazzam Shader Editor http://shazzam-tool.com

  Walt Ritscher : Hmmm. I thought this question was from this week, now I see that it was asked a year ago.