如何優化圖像處理類

Question

我有以下類來處理一個位圖放置魚眼失真。

我已經通過TraceView運行我的應用程序，發現幾乎所有的處理時間都花在循環位圖上。
一位開發人員建議不要使用浮點數，因爲這會降低圖形所關注的部分。還需要使用math.pow（）和ceil（）嗎？
目前通過遍歷整個位圖放置效果大約需要42秒，是秒:)
我試過用整數替換浮動，並已減少時間37秒，但效果是沒有在位圖上存在更長的時間。
arg k最初是一個浮點數，並設置失真的級別，例如0.0002F，如果我傳遞一個int，則該效果不起作用。

任何人都可以指出我如何優化這個過程的正確方向？一旦我優化了它，我想研究一下可能沒有循環遍歷整個位圖，也許會在效果周圍放置邊界框，或者使用下面的算法確定像素是否在半徑爲150的圓內。

class Filters{ 
    float xscale; 
    float yscale; 
    float xshift; 
    float yshift; 
    int [] s; 
    private String TAG = "Filters"; 
    long getRadXStart = 0; 
    long getRadXEnd = 0; 
    long startSample = 0; 
    long endSample = 0; 
    public Filters(){ 

     Log.e(TAG, "***********inside filter constructor"); 
    } 

    public Bitmap barrel (Bitmap input, float k){ 
     //Log.e(TAG, "***********INSIDE BARREL METHOD "); 

     float centerX=input.getWidth()/2; //center of distortion 
     float centerY=input.getHeight()/2; 

     int width = input.getWidth(); //image bounds 
     int height = input.getHeight(); 

     Bitmap dst = Bitmap.createBitmap(width, height,input.getConfig()); //output pic 
     // Log.e(TAG, "***********dst bitmap created "); 
      xshift = calc_shift(0,centerX-1,centerX,k); 

      float newcenterX = width-centerX; 
      float xshift_2 = calc_shift(0,newcenterX-1,newcenterX,k); 

      yshift = calc_shift(0,centerY-1,centerY,k); 

      float newcenterY = height-centerY; 
      float yshift_2 = calc_shift(0,newcenterY-1,newcenterY,k); 

      xscale = (width-xshift-xshift_2)/width; 
     // Log.e(TAG, "***********xscale ="+xscale); 
      yscale = (height-yshift-yshift_2)/height; 
     // Log.e(TAG, "***********yscale ="+yscale); 
     // Log.e(TAG, "***********filter.barrel() about to loop through bm"); 
      /*for(int j=0;j<dst.getHeight();j++){ 
       for(int i=0;i<dst.getWidth();i++){ 
       float x = getRadialX((float)i,(float)j,centerX,centerY,k); 
       float y = getRadialY((float)i,(float)j,centerX,centerY,k); 
       sampleImage(input,x,y); 
       int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff); 
    //   System.out.print(i+" "+j+" \\"); 

       dst.setPixel(i, j, color); 

       } 
      }*/ 

      int origPixel; 
      long startLoop = System.currentTimeMillis(); 
      for(int j=0;j<dst.getHeight();j++){ 
       for(int i=0;i<dst.getWidth();i++){ 
       origPixel= input.getPixel(i,j); 
       getRadXStart = System.currentTimeMillis(); 
       float x = getRadialX((float)j,(float)i,centerX,centerY,k); 
       getRadXEnd= System.currentTimeMillis(); 

       float y = getRadialY((float)j,(float)i,centerX,centerY,k); 

       sampleImage(input,x,y); 

       int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff); 
    //   System.out.print(i+" "+j+" \\"); 

       if(Math.sqrt(Math.pow(i - centerX, 2) + (Math.pow(j - centerY, 2))) <= 150){ 
       dst.setPixel(i, j, color); 
       }else{ 
        dst.setPixel(i,j,origPixel); 
       } 
       } 
      } 
      long endLoop = System.currentTimeMillis(); 
      long loopDuration = endLoop - startLoop; 
      long radXDuration = getRadXEnd - getRadXStart; 
      long sampleDur = endSample - startSample; 

      Log.e(TAG, "sample method took "+sampleDur+"ms"); 
      Log.e(TAG, "getRadialX took "+radXDuration+"ms"); 
      Log.e(TAG, "loop took "+loopDuration+"ms"); 

     // Log.e(TAG, "***********filter.barrel() looped through bm about to return dst bm"); 
     return dst; 
    } 

    void sampleImage(Bitmap arr, float idx0, float idx1) 
    { 
     startSample = System.currentTimeMillis(); 
     s = new int [4]; 
     if(idx0<0 || idx1<0 || idx0>(arr.getHeight()-1) || idx1>(arr.getWidth()-1)){ 
     s[0]=0; 
     s[1]=0; 
     s[2]=0; 
     s[3]=0; 
     return; 
     } 

     float idx0_fl=(float) Math.floor(idx0); 
     float idx0_cl=(float) Math.ceil(idx0); 
     float idx1_fl=(float) Math.floor(idx1); 
     float idx1_cl=(float) Math.ceil(idx1); 

     int [] s1 = getARGB(arr,(int)idx0_fl,(int)idx1_fl); 
     int [] s2 = getARGB(arr,(int)idx0_fl,(int)idx1_cl); 
     int [] s3 = getARGB(arr,(int)idx0_cl,(int)idx1_cl); 
     int [] s4 = getARGB(arr,(int)idx0_cl,(int)idx1_fl); 

     float x = idx0 - idx0_fl; 
     float y = idx1 - idx1_fl; 

     s[0]= (int) (s1[0]*(1-x)*(1-y) + s2[0]*(1-x)*y + s3[0]*x*y + s4[0]*x*(1-y)); 
     s[1]= (int) (s1[1]*(1-x)*(1-y) + s2[1]*(1-x)*y + s3[1]*x*y + s4[1]*x*(1-y)); 
     s[2]= (int) (s1[2]*(1-x)*(1-y) + s2[2]*(1-x)*y + s3[2]*x*y + s4[2]*x*(1-y)); 
     s[3]= (int) (s1[3]*(1-x)*(1-y) + s2[3]*(1-x)*y + s3[3]*x*y + s4[3]*x*(1-y)); 

     endSample = System.currentTimeMillis(); 
    } 

    int [] getARGB(Bitmap buf,int x, int y){ 

     int rgb = buf.getPixel(y, x); // Returns by default ARGB. 
     int [] scalar = new int[4]; 
     scalar[0] = (rgb >>> 24) & 0xFF; 
     scalar[1] = (rgb >>> 16) & 0xFF; 
     scalar[2] = (rgb >>> 8) & 0xFF; 
     scalar[3] = (rgb >>> 0) & 0xFF; 
     return scalar; 
    } 

    float getRadialX(float x,float y,float cx,float cy,float k){ 

     x = (x*xscale+xshift); 
     y = (y*yscale+yshift); 
     float res = x+((x-cx)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy))); 
     return res; 
    } 

    float getRadialY(float x,float y,float cx,float cy,float k){ 

     x = (x*xscale+xshift); 
     y = (y*yscale+yshift); 
     float res = y+((y-cy)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy))); 
     return res; 
    } 

    float thresh = 1; 

    float calc_shift(float x1,float x2,float cx,float k){ 

     float x3 = (float)(x1+(x2-x1)*0.5); 
     float res1 = x1+((x1-cx)*k*((x1-cx)*(x1-cx))); 
     float res3 = x3+((x3-cx)*k*((x3-cx)*(x3-cx))); 

     if(res1>-thresh && res1 < thresh) 
     return x1; 
     if(res3<0){ 
     return calc_shift(x3,x2,cx,k); 
     } 
     else{ 
     return calc_shift(x1,x3,cx,k); 
     } 
    } 



}// end of filters class 

[更新] 我創建了數組作爲實例變量，並在Filter（）構造函數中實例化它們。這是你的意思嗎？該應用程序運行在84秒（錯誤），但現在運行在69秒。似乎也沒有註銷GC。

class Filters{ 
    private float xscale; 
    private float yscale; 
    private float xshift; 
    private float yshift; 
    private int [] s; 
    private int [] scalar; 
    private int [] s1; 
    private int [] s2; 
    private int [] s3; 
    private int [] s4; 
    private String TAG = "Filters"; 
    long getRadXStart = 0; 
    long getRadXEnd = 0; 
    long startSample = 0; 
    long endSample = 0; 
    public Filters(){ 

     Log.e(TAG, "***********inside filter constructor"); 
     s = new int[4]; 
     scalar = new int[4]; 
     s1 = new int[4]; 
     s2 = new int[4]; 
     s3 = new int[4]; 
     s4 = new int[4]; 
    } 

    public Bitmap barrel (Bitmap input, float k){ 
     //Log.e(TAG, "***********INSIDE BARREL METHOD "); 
     Debug.startMethodTracing("barrel"); 

     float centerX=input.getWidth()/2; //center of distortion 
     float centerY=input.getHeight()/2; 

     int width = input.getWidth(); //image bounds 
     int height = input.getHeight(); 

     Bitmap dst = Bitmap.createBitmap(width, height,input.getConfig()); //output pic 
     // Log.e(TAG, "***********dst bitmap created "); 
      xshift = calc_shift(0,centerX-1,centerX,k); 

      float newcenterX = width-centerX; 
      float xshift_2 = calc_shift(0,newcenterX-1,newcenterX,k); 

      yshift = calc_shift(0,centerY-1,centerY,k); 

      float newcenterY = height-centerY; 
      float yshift_2 = calc_shift(0,newcenterY-1,newcenterY,k); 

      xscale = (width-xshift-xshift_2)/width; 
     // Log.e(TAG, "***********xscale ="+xscale); 
      yscale = (height-yshift-yshift_2)/height; 
     // Log.e(TAG, "***********yscale ="+yscale); 
     // Log.e(TAG, "***********filter.barrel() about to loop through bm"); 
      /*for(int j=0;j<dst.getHeight();j++){ 
       for(int i=0;i<dst.getWidth();i++){ 
       float x = getRadialX((float)i,(float)j,centerX,centerY,k); 
       float y = getRadialY((float)i,(float)j,centerX,centerY,k); 
       sampleImage(input,x,y); 
       int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff); 
    //   System.out.print(i+" "+j+" \\"); 

       dst.setPixel(i, j, color); 

       } 
      }*/ 

      int origPixel; 
      long startLoop = System.currentTimeMillis(); 
      for(int j=0;j<dst.getHeight();j++){ 
       for(int i=0;i<dst.getWidth();i++){ 
       origPixel= input.getPixel(i,j); 
       getRadXStart = System.currentTimeMillis(); 
       float x = getRadialX((float)j,(float)i,centerX,centerY,k); 
       getRadXEnd= System.currentTimeMillis(); 

       float y = getRadialY((float)j,(float)i,centerX,centerY,k); 

       sampleImage(input,x,y); 

       int color = ((s[1]&0x0ff)<<16)|((s[2]&0x0ff)<<8)|(s[3]&0x0ff); 
    //   System.out.print(i+" "+j+" \\"); 

       if(Math.sqrt(Math.pow(i - centerX, 2) + (Math.pow(j - centerY, 2))) <= 150){ 
       dst.setPixel(i, j, color); 
       }else{ 
        dst.setPixel(i,j,origPixel); 
       } 
       } 
      } 
      long endLoop = System.currentTimeMillis(); 
      long loopDuration = endLoop - startLoop; 
      long radXDuration = getRadXEnd - getRadXStart; 
      long sampleDur = endSample - startSample; 

      Log.e(TAG, "sample method took "+sampleDur+"ms"); 
      Log.e(TAG, "getRadialX took "+radXDuration+"ms"); 
      Log.e(TAG, "loop took "+loopDuration+"ms"); 

     // Log.e(TAG, "***********filter.barrel() looped through bm about to return dst bm"); 
      Debug.stopMethodTracing(); 
     return dst; 

    } 

    void sampleImage(Bitmap arr, float idx0, float idx1) 
    { 
     startSample = System.currentTimeMillis(); 
     // s = new int [4]; 
     if(idx0<0 || idx1<0 || idx0>(arr.getHeight()-1) || idx1>(arr.getWidth()-1)){ 
     s[0]=0; 
     s[1]=0; 
     s[2]=0; 
     s[3]=0; 
     return; 
     } 

     float idx0_fl=(float) Math.floor(idx0); 
     float idx0_cl=(float) Math.ceil(idx0); 
     float idx1_fl=(float) Math.floor(idx1); 
     float idx1_cl=(float) Math.ceil(idx1); 

    /* int [] s1 = getARGB(arr,(int)idx0_fl,(int)idx1_fl); 
     int [] s2 = getARGB(arr,(int)idx0_fl,(int)idx1_cl); 
     int [] s3 = getARGB(arr,(int)idx0_cl,(int)idx1_cl); 
     int [] s4 = getARGB(arr,(int)idx0_cl,(int)idx1_fl);*/ 

     s1 = getARGB(arr,(int)idx0_fl,(int)idx1_fl); 
     s2 = getARGB(arr,(int)idx0_fl,(int)idx1_cl); 
     s3 = getARGB(arr,(int)idx0_cl,(int)idx1_cl); 
     s4 = getARGB(arr,(int)idx0_cl,(int)idx1_fl); 

     float x = idx0 - idx0_fl; 
     float y = idx1 - idx1_fl; 

     s[0]= (int) (s1[0]*(1-x)*(1-y) + s2[0]*(1-x)*y + s3[0]*x*y + s4[0]*x*(1-y)); 
     s[1]= (int) (s1[1]*(1-x)*(1-y) + s2[1]*(1-x)*y + s3[1]*x*y + s4[1]*x*(1-y)); 
     s[2]= (int) (s1[2]*(1-x)*(1-y) + s2[2]*(1-x)*y + s3[2]*x*y + s4[2]*x*(1-y)); 
     s[3]= (int) (s1[3]*(1-x)*(1-y) + s2[3]*(1-x)*y + s3[3]*x*y + s4[3]*x*(1-y)); 

     endSample = System.currentTimeMillis(); 
    } 

    int [] getARGB(Bitmap buf,int x, int y){ 

     int rgb = buf.getPixel(y, x); // Returns by default ARGB. 
     // int [] scalar = new int[4]; 
     scalar[0] = (rgb >>> 24) & 0xFF; 
     scalar[1] = (rgb >>> 16) & 0xFF; 
     scalar[2] = (rgb >>> 8) & 0xFF; 
     scalar[3] = (rgb >>> 0) & 0xFF; 
     return scalar; 
    } 

    float getRadialX(float x,float y,float cx,float cy,float k){ 

     x = (x*xscale+xshift); 
     y = (y*yscale+yshift); 
     float res = x+((x-cx)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy))); 
     return res; 
    } 

    float getRadialY(float x,float y,float cx,float cy,float k){ 

     x = (x*xscale+xshift); 
     y = (y*yscale+yshift); 
     float res = y+((y-cy)*k*((x-cx)*(x-cx)+(y-cy)*(y-cy))); 
     return res; 
    } 

    float thresh = 1; 

    float calc_shift(float x1,float x2,float cx,float k){ 

     float x3 = (float)(x1+(x2-x1)*0.5); 
     float res1 = x1+((x1-cx)*k*((x1-cx)*(x1-cx))); 
     float res3 = x3+((x3-cx)*k*((x3-cx)*(x3-cx))); 

     if(res1>-thresh && res1 < thresh) 
     return x1; 
     if(res3<0){ 
     return calc_shift(x3,x2,cx,k); 
     } 
     else{ 
     return calc_shift(x1,x3,cx,k); 
     } 
    } 



}// end of filters class 

Answer 1

從我所看到的，你的代碼執行以下操作：

for (every pixel in bitmap){ 
    getPixel(); 
    ...do something to pixel... 
    setPixel(); 
} 

的getPixel()和setPixel()函數調用相對昂貴。您可以嘗試使用getPixels()將所有像素放入數組，然後通過數組訪問每個像素，而不是在循環中反覆調用它們。請參閱此answer。

如果仍然不夠，請嘗試使用C++編碼NDK。

Answer 2

有一兩件事你可以嘗試是避免由兩個嵌套的循環外，一旦實例並將其傳遞到這些方法創建/重建在「sampleImage」和「getARGB」整型數組。從代碼可維護性的角度來看，這不是最佳實踐。但是，它會避免重複創建對象，數組初始化和垃圾收集開銷。這些代碼往往比其餘代碼中的算術運算要昂貴得多。

Answer 3

首先 - 衡量你的函數的一些部分，看看瓶頸在哪裏。不要試圖通過猜測來優化。

說了這麼多，我現在就嘗試說任務:)

做一個sqrt()每個像素是相當昂貴的 - 你是比較恆定的，所以不是，方恆和比較平方值即：

if((Math.pow(i - centerX, 2) + (Math.pow(j - centerY, 2))) <= 150*150){ 

而且使用pow(x,2)方的東西可能是調用庫函數爲pow()，將您float s到double，但在進行通用動力提升算法和轉換回float秒。改爲使用x*x。

if(((i-centerX)*(i-centerX) + (j-centerY)*(j-centerY)) <= 150){