c++ - How can I flip a buffer vertically during an YUV to RGB conversion -
edit : question not clear sorry, updated , added details.
i have buffer image data (yuv format) convert rgb format. problem is, flip image vertically (invert y-position).
what i'm able moment convert yuv data rgb data in buffer, flip buffer vertically.
here working code :
unsigned char* decklinkcapturedelegate::convertyuvtorgb(void* framebytes) { unsigned char *mycopy = new unsigned char[height*width*3]; unsigned char *flippedcopy = new unsigned char[height*width*3]; unsigned char* pdata = (unsigned char *) framebytes; //conversion yuv rgb for(int = 0, j=0; < width * height * 3; i+=6, j+=4) { unsigned char v = pdata[j]; unsigned char y = pdata[j+1]; unsigned char u = pdata[j+2]; mycopy[i+2] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[i+1] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[i] = 1.0*y + 1.772*(u-128) + 0; // b y = pdata[j+3]; mycopy[i+5] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[i+4] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[i+3] = 1.0*y + 1.772*(u-128) + 0; } //vertical flip (int = 0; < width; ++i) { (int j = 0; j < height; ++j) { (int k = 0; k < 3; ++k) { flippedcopy[(i + j * width) * 3 + k] = mycopy[(i + (height - 1 - j) * width) * 3 + k]; } } } return flippedcopy; } what gain performance flip buffer during conversion yuv rgb. had no idea how , yusuf answer helped me, here have moment :
unsigned char* decklinkcapturedelegate::convertyuvtorgb(void* framebytes) { unsigned char *mycopy = new unsigned char[height*width*3]; unsigned char* pdata = (unsigned char *) framebytes; int k = height - 1; for(int = 0, j=0; < width * height * 3; i+=6, j+=4) { unsigned char v = pdata[j]; unsigned char y = pdata[j+1]; unsigned char u = pdata[j+2]; mycopy[(width*k*3) + i+2] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[(width*k*3) + i+1] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[(width*k*3) + i] = 1.0*y + 1.772*(u-128) + 0; // b y = pdata[j+3]; mycopy[(width*k*3) + i+5] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[(width*k*3) + i+4] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[(width*k*3) + i+3] = 1.0*y + 1.772*(u-128) + 0; if (<i multiple of (width*3)-1>){ k = k - 2; } } return mycopy; } if i'm correct, should work, assuming if condition right. don't know how express if condition, since i incremented 6 each time, might "skip" right moment decrement k
i hope i'm clear enough. thanks
i assume width even, otherwise "reduce in new line"-if complicated, must use 2 loops. didn't tested, should this;
unsigned char* decklinkcapturedelegate::convertyuvtorgb(void* framebytes) { unsigned char *mycopy = new unsigned char[height*width*3]; unsigned char* pdata = (unsigned char *) framebytes; unsigned int k = height - 1; for(int = 0, j=0; < width * height * 3; i+=6, j+=4) { unsigned char v = pdata[j]; unsigned char y = pdata[j+1]; unsigned char u = pdata[j+2]; mycopy[(width*k*3) + i+2] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[(width*k*3) + i+1] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[(width*k*3) + i] = 1.0*y + 1.772*(u-128) + 0; // b y = pdata[j+3]; mycopy[(width*k*3) + i+5] = 1.0*y + 8 + 1.402*(v-128); // r mycopy[(width*k*3) + i+4] = 1.0*y - 0.34413*(u-128) - 0.71414*(v-128); // g mycopy[(width*k*3) + i+3] = 1.0*y + 1.772*(u-128) + 0; if (mod(i, width*3) == 0) //reduce in new line (i not sure how reduce it, should think here) k = k - 2; } return mycopy; } and tag question imageprocessing etc not c++
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