我有以下类来处理Bitmap以在其上放置鱼眼失真。
我通过TraceView运行我的应用程序，发现几乎所有处理时间都花在循环遍历位图上。
一位开发人员建议不使用float，因为这会降低图形的速度。还需要使用math.pow（）和ceil（）吗？
目前通过循环整个位图来放置效果需要大约42秒，是秒秒:)
我尝试用整数替换浮点数并将时间缩短到37秒，但效果不再出现在位图上。
arg k最初是一个浮点数并设置失真级别，例如0.0002F，如果我传递一个int，效果不起作用。
有人能指出我如何优化这一过程的正确方向吗？一旦我对它进行了优化，我想调查可能不会遍历整个位图，并且可能在效果周围放置一个边界框，或者使用下面的算法确定像素是否在半径为150的圆内。
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] 我已经将数组创建为实例变量，并在Filter（）构造函数中实例化它们。这是你的意思吗？应用程序运行时间为84秒（错误），但现在运行时间为69秒。似乎没有GC退出。
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
答案 0 :(得分：2)
首先关闭 - 测量功能的某些部分，看看瓶颈在哪里。不要试图通过猜测来优化。
话虽如此，我现在将尝试完成任务：）
每个像素执行sqrt()非常昂贵 - 您要与常量进行比较，因此，将常数平方并将平方值与之比较：
if( ( Math.pow(i - centerX, 2) + ( Math.pow(j - centerY, 2) ) ) <= 150*150 ){
同样使用pow(x,2)来解决某些事情可能会调用pow()的库函数，将float转换为double s，进行通用功率提升算法并转换回float s。只需使用x*x代替。
if(((i-centerX)*(i-centerX) + (j-centerY)*(j-centerY)) <= 150){
答案 1 :(得分：1)
从我看到的，您的代码正在执行以下操作：
for (every pixel in bitmap){
getPixel();
...do something to pixel...
setPixel();
}
getPixel()和setPixel()函数调用相对较贵。您可以尝试使用getPixels()将所有像素放入数组中，然后通过数组访问每个像素，而不是在循环中一遍又一遍地调用它们。请参阅此answer。
如果仍然不够，请尝试通过NDK。
在C ++中对上述内容进行编码答案 2 :(得分：0)
您可能尝试的一件事是避免在'sampleImage'和'getARGB'中创建/重新创建int数组，方法是在两个嵌套循环之外实例化它们并将它们传递给这些方法。从代码可维护性的角度来看，这不是最佳实践。但是，它将避免重复的对象创建，数组初始化和垃圾收集开销。这些代码往往比代码的其余部分中的算术运算成本高得多。