标签：vip base signed dht jad icp pcr ns2 urb
简单实现, 仅限单通道图像
双向性差值中，缩放图像(以下称目标图像)的像素的点 P 的强度值取决于相邻4个像素点的加权和。
假设缩放因子为 s, 那么目标图像的像素点可以通过 r, c 来映射源图像，如下所示
那么从感兴趣像素点到原图像像素的距离可如下表示
因此相邻4个像素点可表示为
然后利用上述信息，可以计算出感兴趣像素点值的加权和
代码如下所示：
1 void resize_zoom(unsigned char *pSrc, unsigned char *pDst, int src_stride, int src_height, float zoom_x, float zoom_y) 2 { 3 #define CHECK_BOUNDARY(a, v) ((a) > (v) ? (v):( (a) <0 ? (0):(a) )) 4 if (!(zoom_x > 0 && zoom_y > 0 && src_stride > 0 && src_height > 0 && pSrc != NULL && pDst != NULL)) { 5 printf("input param error..\n"); 6 pDst = NULL; 7 return; 8 } 9 int dst_w = floor(zoom_x * src_stride); 10 int dst_h = floor(zoom_y * src_height); 11 12 for (int h = 0; h < dst_h; h++) { 13 int y1 = CHECK_BOUNDARY(floor(h / zoom_y), src_height); 14 int y2 = CHECK_BOUNDARY(ceil(h / zoom_y), src_height); 15 float y = fmod((h/zoom_y), 1); 16 for (int w = 0; w < dst_w; w++) { 17 int x1 = CHECK_BOUNDARY(floor(w / zoom_x), src_stride); 18 int x2 = CHECK_BOUNDARY(ceil(w / zoom_x), src_stride); 19 float x = fmod((w / zoom_x), 1); 20 unsigned char topLeft = pSrc[y1 * src_stride + x1]; 21 unsigned char botLeft = pSrc[y1 * src_stride + x2]; 22 unsigned char topRight = pSrc[y2 * src_stride + x1]; 23 unsigned char botRight = pSrc[y2 * src_stride + x2]; 24 unsigned int tr = (topRight * y) + (topLeft * (1 - y)); 25 unsigned int br = (botRight * y) + (botLeft * (1 - y)); 26 unsigned int c = (br * x) + (tr * (1 - x)); 27 pDst[h * dst_w + w] = CHECK_BOUNDARY(c, 255); 28 } 29 } 30 #undef CHECK_BOUNDARY 31 }
最近邻插值算法中，像素点 v(x, y) 的强度取决于该点映射到源图像素点 f(x, y) 相邻像素的强度值。
具体实现逻辑如下
1 void nnbr(unsigned char *pSrc, unsigned char *pDst, int src_stride, int src_height, float zoom_x, float zoom_y) 2 { 3 #define CHECK_BOUNDARY(a, v) ((a) > (v) ? (v):( (a) <0 ? (0):(a) )) 4 if (!(zoom_x > 0 && zoom_y > 0 && src_stride > 0 && src_height > 0 && pSrc != NULL && pDst != NULL)) { 5 printf("input param error..\n"); 6 pDst = NULL; 7 return; 8 } 9 int dst_w = floor(zoom_x * src_stride); 10 int dst_h = floor(zoom_y * src_height); 11 12 for (int h = 0; h < dst_h; h++) { 13 int near_h = CHECK_BOUNDARY(floor(h / zoom_y), src_height); 14 for (int w = 0; w < dst_w; w++) { 15 int near_w = CHECK_BOUNDARY(floor(w / zoom_x), src_stride); 16 unsigned int c = pSrc[near_h * src_stride + near_w]; 17 pDst[h * dst_w + w] = CHECK_BOUNDARY(c, 255); 18 } 19 } 20 #undef CHECK_BOUNDARY 21 }
标签：vip base signed dht jad icp pcr ns2 urb
原文地址：http://www.cnblogs.com/openxyz/p/6664595.html
