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我正在尝试让 Silverlight 的 HLSL 像素着色器工作以从视频图像中减去背景图像。谁能建议一个比我使用的更复杂的算法，因为我的算法没有正确执行？

float Tolerance : register(C1);
SamplerState  ImageSampler : register(S0);
SamplerState  BackgroundSampler : register(S1);

struct VS_INPUT
{
    float4 Position : POSITION;
    float4 Diffuse  : COLOR0;
    float2 UV0      : TEXCOORD0;
    float2 UV1      : TEXCOORD1;
};

struct VS_OUTPUT
{
    float4 Position  : POSITION;
    float4 Color     : COLOR0;
    float2 UV        : TEXCOORD0;
};


float4 PS( VS_OUTPUT input ) : SV_Target
{
    float4 color = tex2D( ImageSampler, input.UV );
    float4 background = tex2D( BackgroundSampler, input.UV);

    if (abs(background.r - color.r) <= Tolerance && 
                  abs(background.g - color.g) <= Tolerance && 
                  abs(background.b - color.b) <= Tolerance)
    {
      color.rgba = 0;
    }

   return color;

}

要查看此示例，您需要一台带网络摄像头的计算机：

  1. 转到页面http://xmldocs.net/alphavideo/background.html
  2. 按[开始录制]。
  3. 将您的身体移出场景，然后按 [捕获背景]。
  4. 然后将您的身体移回场景中并使用滑块将 Toleance 值调整到着色器。
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1 回答 1

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EDIT

Single pixel isn't useful for such task, because of noise. So algorithm essence should be to measure similarity between pixel blocks. Recipe pseudo-code (based on correlation measurement):

Divide image into N x M grid
For each N,M cell in grid:
   correlation = correlation_between(signal_pixels_of(N,M),
                                     background_pixels_of(N,M)
                                    );
   if (correlation > threshold)
      show_background_cell(N,M)
   else
      show_signal_cell(N,M)

This is sequential pseudo code, but it could be easily converted to HLSL shader. Simply each pixel detects to which pixel block it belongs, and after that measures correlation between corresponding blocks. And based on that correlation shows or hides current pixel.

Try this approach, Good Luck !

于 2010-09-06T10:12:50.577 回答