使用EasyBMP進行雙三次插值不能正常工作

Question

我正在編寫一個使用雙三次插值的程序，並且使用EasyBMP，但是我遇到了問題。輸入圖像是peppers。

我的輸出看起來像this。

#define BOUNDS(val, min, max) if (val < min) { val = min; } else if (val > max) { val = max; } 

void resize(float value) 
{ 
    BMP* temp = new BMP(); 
    int in_w = image->TellWidth(); 
    int in_h = image->TellHeight(); 
    temp->SetSize(in_w*value, in_h*value); 
    RGBApixel input; 

    for (int y = 0; y < temp->TellHeight(); ++y) 
    { 
     float v = float(y)/float(temp->TellHeight() - 1); 
     for (int x = 0; x < temp->TellWidth(); ++x) 
     { 
      float u = float(x)/float(temp->TellWidth() - 1); 

      input = this->bicubicInterpolation(u,v); 

      temp->SetPixel(x,y,input); 
     } 
    } 

    delete image; 
    image=temp; 
} 


RGBApixel bicubicInterpolation(float u, float v) 
{ 
    RGBApixel p[4][4]; 
    int q,w; 

    float x = (u * image->TellWidth()) - 0.5; 
    int xint = int(x); 
    float dx = x - floor(x); 

    float y = (v * image->TellHeight()) - 0.5; 
    int yint = int(y); 
    float dy = y - floor(y); 

    for(int i=0; i<4; i++) 
    { 
     for(int j=0; j<4; j++) 
     { 
      q=xint - 1 + j; 
      BOUNDS(q,0,image->TellWidth()-1) 
      w=yint - 1 + i; 
      BOUNDS(w,0,image->TellHeight()-1) 
      p[j][i] = image->GetPixel(q,w); 
     } 
    } 
    RGBApixel toReturn; 
    RGBApixel el1 = this->interpolation(p[0][0],p[1][0], p[2][0], p[3][0], dx); 
    RGBApixel el2 = this->interpolation(p[0][1],p[1][1], p[2][1], p[3][1], dx); 
    RGBApixel el3 = this->interpolation(p[0][2],p[1][2], p[2][2], p[3][2], dx); 
    RGBApixel el4 = this->interpolation(p[0][3],p[1][3], p[2][3], p[3][3], dx); 
    RGBApixel value = this->interpolation(el1, el2, el3, el4, dy); 

    return value; 
} 

RGBApixel interpolation(RGBApixel A, RGBApixel B, RGBApixel C, RGBApixel D, float t) 
{ 
    float a[3],b[3],c[3],d[3]; 
    RGBApixel toRet; 
    a[0]=A.Red; 
    b[0]=B.Red; 
    c[0]=C.Red; 
    d[0]=D.Red; 

    a[1]=A.Green; 
    b[1]=B.Green; 
    c[1]=C.Green; 
    d[1]=D.Green; 

    a[2]=A.Blue; 
    b[2]=B.Blue; 
    c[2]=C.Blue; 
    d[2]=D.Blue; 

    float w[3]; 
    float x[3]; 
    float y[3]; 
    float z[3]; 

    float color[3]; 

    for(int i=0; i<3; i++) 
    { 
     w[i]= -a[i]/2.0f + (3.0f*b[i])/2.0f - (3.0f*c[i])/2.0f + d[i]/2.0f; 
     x[i]= a[i] - (5.0f*b[i])/2.0f + 2.0f*c[i] - d[i]/2.0f; 
     y[i]= -a[i]/2.0f + c[i]/2.0f; 
     z[i]= b[i]; 
     color[i]= w[i] * t*t*t + x[i] * t*t + y[i] * t +z[i]; 
    } 
    toRet.Red=color[0]; 
    toRet.Green=color[1]; 
    toRet.Blue=color[2]; 
    toRet.Alpha=255; 

    return toRet; 
} 

你有沒有注意到我犯的錯誤？

Answer 1

這是超出範圍。只需要：

color[i]= w[i] * t*t*t + x[i] * t*t + y[i] * t +z[i]; 
BOUNDS(color[i],0,255);