我正在ARM上工作,並且我正在嘗試優化縮減採樣圖像,我已經使用OpenCV cv :: resize和其緩慢〜3ms的1280 * 960到400 * 300,我正在嘗試使用OpenMP來加速它,但是,在放置並行語句時,圖像已被扭曲。我知道這與線程之間的私有變量和共享數據有關,但我找不到問題。使用OpenMP來優化雙線性插值
void resizeBilinearGray(uint8_t *pixels, uint8_t *temp, int w, int h, int w2, int h2) {
int A, B, C, D, x, y, index, gray ;
float x_ratio = ((float)(w-1))/w2 ;
float y_ratio = ((float)(h-1))/h2 ;
float x_diff, y_diff;
int offset = 0 ;
#pragma omp parallel for
for (int i=0;i<h2;i++) {
for (int j=0;j<w2;j++) {
x = (int)(x_ratio * j) ;
y = (int)(y_ratio * i) ;
x_diff = (x_ratio * j) - x ;
y_diff = (y_ratio * i) - y ;
index = y*w+x ;
// range is 0 to 255 thus bitwise AND with 0xff
A = pixels[index] & 0xff ;
B = pixels[index+1] & 0xff ;
C = pixels[index+w] & 0xff ;
D = pixels[index+w+1] & 0xff ;
// Y = A(1-w)(1-h) + B(w)(1-h) + C(h)(1-w) + Dwh
gray = (int)(
A*(1-x_diff)*(1-y_diff) + B*(x_diff)*(1-y_diff) +
C*(y_diff)*(1-x_diff) + D*(x_diff*y_diff)
) ;
temp[offset++] = gray ;
}
}
}
所以你認爲我,K應該是私人變量?另一個嵌套循環呢? 我嘗試後,我會嘗試ARM霓虹燈 – 2013-03-16 12:41:54
我和j已經是私人變量,因爲它是在openmp編譯後定義的。你有沒有嘗試我的建議? – 2013-03-16 13:15:22
如果您想了解更多關於循環嵌套的信息,請參閱此鏈接。但它不會解決您的圖像失真問題。這是由於你如何使用偏移量。你需要用temp [i * w2 + j]替換temp [offset ++] http://bisqwit.iki.fi/story/howto/openmp/#ReductionClause – 2013-03-16 13:19:52