編輯:在Windows平臺上工作。將矩陣應用於圖像,尋求性能改進
問題:問題較少,更多關於建議。我目前對低級程序並不熟悉,但我試圖優化下面的代碼,試圖提高整體代碼的性能。此應用程序取決於極高速度的圖像處理。
當前性能:在我的電腦上,目前計算512x512圖像的時間大約是4-6ms。如果可能的話,我試圖減少一半。
限制:由於此項目規模巨大,對應用程序根本的變化是非常困難的事,這樣的事情,如移植到DirectX或其它GPU方法並不多一種選擇。該項目目前有效,我只是想弄清楚如何讓它工作得更快。
我的這種用途的具體信息:圖片進入這個方法總是會正好廣場和128 (最有可能的512×512)一些增量,他們總是會出來一樣大小。除此之外,沒有其他的東西了。矩陣是在其他地方計算的,所以這只是將矩陣應用於我的圖像。原始圖像和新圖像都正在使用,因此需要複製圖像。
這是我目前的執行:
void ReprojectRectangle(double *mpProjMatrix, unsigned char *pDstScan0, unsigned char *pSrcScan0,
int NewBitmapDataStride, int SrcBitmapDataStride, int YOffset, double InversedAspect, int RectX, int RectY, int RectW, int RectH)
{
int i, j;
double Xnorm, Ynorm;
double Ynorm_X_ProjMatrix4, Ynorm_X_ProjMatrix5, Ynorm_X_ProjMatrix7;;
double SrcX, SrcY, T;
int SrcXnt, SrcYnt;
int SrcXec, SrcYec, SrcYnvDec;
unsigned char *pNewPtr, *pSrcPtr1, *pSrcPtr2, *pSrcPtr3, *pSrcPtr4;
int RectX2, RectY2;
/* Compensate (or re-center) the Y-coordinate regarding the aspect ratio */
RectY -= YOffset;
/* Compute the second point of the rectangle for the loops */
RectX2 = RectX + RectW;
RectY2 = RectY + RectH;
/* Clamp values (be careful with aspect ratio */
if (RectY < 0) RectY = 0;
if (RectY2 < 0) RectY2 = 0;
if ((double)RectY > (InversedAspect * 512.0)) RectY = (int)(InversedAspect * 512.0);
if ((double)RectY2 > (InversedAspect * 512.0)) RectY2 = (int)(InversedAspect * 512.0);
/* Iterate through each pixel of the scaled re-Proj */
for (i=RectY; i<RectY2; i++)
{
/* Normalize Y-coordinate and take the ratio into account */
Ynorm = InversedAspect - (double)i/512.0;
/* Pre-compute some matrix coefficients */
Ynorm_X_ProjMatrix4 = Ynorm * mpProjMatrix[4] + mpProjMatrix[12];
Ynorm_X_ProjMatrix5 = Ynorm * mpProjMatrix[5] + mpProjMatrix[13];
Ynorm_X_ProjMatrix7 = Ynorm * mpProjMatrix[7] + mpProjMatrix[15];
for (j=RectX; j<RectX2; j++)
{
/* Get a pointer to the pixel on (i,j) */
pNewPtr = pDstScan0 + ((i+YOffset) * NewBitmapDataStride) + j;
/* Normalize X-coordinates */
Xnorm = (double)j/512.0;
/* Compute the corresponding coordinates in the source image, before Proj and normalize source coordinates*/
T = (Xnorm * mpProjMatrix[3] + Ynorm_X_ProjMatrix7);
SrcY = (Xnorm * mpProjMatrix[0] + Ynorm_X_ProjMatrix4)/T;
SrcX = (Xnorm * mpProjMatrix[1] + Ynorm_X_ProjMatrix5)/T;
// Compute the integer and decimal values of the coordinates in the sources image
SrcXnt = (int) SrcX;
SrcYnt = (int) SrcY;
SrcXec = 64 - (int) ((SrcX - (double) SrcXnt) * 64);
SrcYec = 64 - (int) ((SrcY - (double) SrcYnt) * 64);
// Get the values of the four pixels up down right left
pSrcPtr1 = pSrcScan0 + (SrcXnt * SrcBitmapDataStride) + SrcYnt;
pSrcPtr2 = pSrcPtr1 + 1;
pSrcPtr3 = pSrcScan0 + ((SrcXnt+1) * SrcBitmapDataStride) + SrcYnt;
pSrcPtr4 = pSrcPtr3 + 1;
SrcYnvDec = (64-SrcYec);
(*pNewPtr) = (unsigned char)(((SrcYec * (*pSrcPtr1) + SrcYnvDec * (*pSrcPtr2)) * SrcXec +
(SrcYec * (*pSrcPtr3) + SrcYnvDec * (*pSrcPtr4)) * (64 - SrcXec)) >> 12);
}
}
}
在Windows上工作。感謝提示,我會研究這些。多處理似乎需要更多時間來解析圖像並將其發送到每個進程。但我可能是錯的。 – Corylulu