sdl_yuv.rar_JPEG YUV_libjpeg yuv _yuv jpeg_yuv的缩放_yuv缩放

YUV 任意尺寸缩放2011-11-20 16:52最近项目中遇到jpeg 图片缩放问题，libjpeg 只支持 1/8, 1/4, 1/2, 1/1 的缩小。而 ffplay 对 Jpeg, 视频的缩放貌似不支持。 于是经过断断续续的编码和思考，“基本上” 解决了YUV420P格式的缩放问题。 这里的“基本上”指的是： 1）它解决了视频全屏缩小问题，没有产生颜色偏移等问题； 2）YUV 按某一特定比例对静态图缩放后，颜色可能会变； 代码： /*file:sdl_yuv.c direct access yuv color space author: ludi gcc sdl_yuv.c rgb2yuv.c -g -DGEN_SDL_YUV_EXE `sdl-config --cflags --libs` quick and dirty, but it is correct: void drawHLine_(SDL_Overlay *yuv, int sx, int sy, int len) { int w = yuv->pitches[0]; memset(yuv->pixels[0]+sy*w + sx, 255, len*1); memset(yuv->pixels[1]+(sy*w + 2*sx)/4, 255, (len+1)/2); memset(yuv->pixels[2]+(sy*w + 2*sx)/4, 255, (len+1)/2); } todo: add scalability for blitSurface2YUV (really need this??). history: 2011.11.05 initial startup. */ #include<string.h> #include<SDL.h> /* 双线性内插值算法描述如下: 对于一个目的像素，设置坐标通过反向变换得到的浮点坐标为(i+u,j+v) (其中i、j均为浮点坐标的整数部分，u、v为浮点坐标的小数部分，是取值[0,1)区间的浮点数)， 则这个像素的值 f(i+u,j+v) 可由原图像中坐标为 (i,j)、(i+1,j)、(i,j+1)、(i+1,j+1)所对应的周围四个像素的值决定，即： 　　f(i+u,j+v) = (1-u)(1-v)f(i,j) + (1-u)vf(i,j+1) + u(1-v)f(i+1,j) + uvf(i+1,j+1) 公式1 其中f(i,j)表示源图像(i,j)处的的像素值，以此类推。 例子： 假如目标图的象素坐标为（1，1），那么反推得到的对应于源图的坐标是（0.75 , 0.75）, 这其实只是一个概念上的虚拟象素,实际在源图中并不存在这样一个象素, 那么目标图的象素（1，1）的取值不能够由这个虚拟象素来决定， 而只能由源图的这四个象素共同决定：（0，0）（0，1）（1，0）（1，1）， 而由于（0.75,0.75）离（1，1）要更近一些，那么（1,1）所起的决定作用更大一些， 这从公式1中的系数uv=0.75×0.75就可以体现出来， 而（0.75,0.75）离（0，0）最远，所以（0，0）所起的决定作用就要小一些， 公式中系数为(1-u)(1-v)=0.25×0.25也体现出了这一特点； 浮点运算的优化： 反向变换 (x, y) --> (i+u, j+v) = (sw/dw * x, sh/dh * y) u = (sw*x % dw)/dw v = (sh*y % dh)/dh 1 - u = (dw - sw*x % dw)/dw 1 - v = (dh - sh*y % dh)/dh 公式1 f(i+u,j+v) = (1-u)(1-v)f(i,j) + (1-u)vf(i,j+1) + u(1-v)f(i+1,j) + uvf(i+1,j+1) 两边同时乘以 dw*dh,得到 dw*dh*f(i+u, j+v) = (dw - sw*x % dw)*(dh - sh*y %dh)*f(i,j) + ... + (sw*x % dw)(sh*y % dh)f(i+1,j+1) * */ #define yf(i,j) (*((Uint8*)src->pixels[0] + ((j) + srcrect->y)*src->pitches[0] + ((i) + srcrect->x) )) #define vf(i,j) (*((Uint8*)src->pixels[1] + ((j)/2 + srcrect->y/2)*src->pitches[1] + ((i)/2 + srcrect->x/2) )) #define uf(i,j) (*((Uint8*)src->pixels[2] + ((j)/2 + srcrect->y/2)*src->pitches[2] + ((i)/2 + srcrect->x/2) )) int blitYUV2YUVScale(SDL_Overlay *src, SDL_Rect *srcrect, SDL_Overlay *dst, SDL_Rect *dstrect) { unsigned int x,y, i,j, tu,tv,tu1,tv1,tf; unsigned int y1,v1,u1; int dw,dh, sw,sh; //check args if(src->format != dst->format)return 1; dw = dstrect->x + dstrect->w < dst->w ? dstrect->w : dst->w - dstrect->x; dh = dstrect->y + dstrect->h < dst->h ? dstrect->h : dst->h - dstrect->y; sw = srcrect->x + srcrect->w < src->w ? srcrect->w : src->w - srcrect->x; sh = srcrect->y + srcrect->h < src->h ? srcrect->h : src->h - srcrect->y; if(dw <= 0 || dh <= 0 || sw <= 0 || sh <= 0) return 1; for(y = 0; y < dh; ++y) { for(x = 0; x < dw; ++x) { i = sw*x / dw; j = sh*y / dh; tu = sw*x % dw; tv = sh*y % dh; tu1 = dw - tu; tv1 = dh - tv; tf = tu1 * tv1 * yf(i,j) + tu1 * tv * yf(i,j+1) + tu * tv1 * yf(i+1,j) + tu * tv * yf(i+1,j+1); y1 = tf/(dw*dh); *(dst->pixels[0] + (dstrect->y + y) * dst->pitches[0] + (dstrect->x + x)) = y1; if((x%2 == 0 ) && (y%2 == 0 )) { tf = tu1 * tv1 * vf(i,j) + tu1 * tv * vf(i,j+1) + tu * tv1 * vf(i+1,j) + tu * tv * vf(i+1,j+1); v1 = tf/(dw*dh); tf = tu1 * tv1 * uf(i,j) + tu1 * tv * uf(i,j+1) + tu * tv1 * uf(i+1,j) + tu * tv * uf(i+1,j+1); u1 = tf/(dw*dh); *(dst->pixels[1] + (y/2 + dstrect->y /2) * dst->pitches[1] + (dstrect->x/2 + x/2)) = v1; *(dst->pixels[2] + (y/2 + dstrect->y /2) * dst->pitches[2] + (dstrect->x/2 + x/2)) = u1; } } } return 0; } extern void rgb2yuv(int r, int g, int b, int *y, int *u, int *v); extern void yuv2rgb(int y, int u, int v, int *r, int *g, int *b); void fillRect(SDL_Overlay *yuv, SDL_Rect *rect, int y0, int u, int v) { int y; int size = rect->w; int uv_size = (size-1)/2+1; int uv_off = 0; for(y = 0; y< rect->h; ++y) { memset(yuv->pixels[0] + (rect->y + y) * yuv->pitches[0] + rect->x, y0, size); if(y%2 == 0) { memset(yuv->pixels[1] + (uv_off + rect->y /2) * yuv->pitches[1] + rect->x/2, v, uv_size); memset(yuv->pixels[2] + (uv_off + rect->y /2) * yuv->pitches[2] + rect->x/2, u, uv_size); ++uv_off; } } } int blitYUV2YUV(SDL_Overlay *src, int srcx, int srcy, SDL_Overlay *dst, SDL_Rect *dstrect) { int min_size, uv_size, min_h, line, uv_off; min_size = (src->pitches[0] - srcx < dst->pitches[0] - dstrect->x)? src->pitches[0] - srcx : dst->pitches[0] - dstrect->x; min_h = (src->h - srcy < dst->h - dstrect->y)? src->h - srcy : dst->h - dstrect->y; if(min_size > dstrect->w ) min_size = dstrect->w; if(min_h > dstrect->h)min_h = dstrect->h; if(min_size <= 0 || min_h <= 0)return 0; if(src->format != dst->format)return 1; for(uv_off = 0, line = 0; line < min_h; line++) { memcpy(dst->pixels[0] + (line + dstrect->y) * dst->pitches[0] + dstrect->x, src->pixels[0] + (line + srcy) * src->pitches[0] + srcx, min_size); if(line%2 == 0) { uv_size = (min_size+1)/2; memcpy(dst->pixels[1] + (uv_off + dstrect->y /2) * dst->pitches[1] + dstrect->x /2, src->pixels[1] + (uv_off + srcy /2) * src->pitches[1] + srcx /2, uv_size); memcpy(dst->pixels[2] + (uv_off + dstrect->y /2) * dst->pitches[2] + dstrect->x /2, src->pixels[2] + (uv_off + srcy /2) * src->pitches[2] + srcx /2, uv_size); ++uv_off; } } return 0; } int blitSurface2YUV(SDL_Surface *src, SDL_Overlay *dst, SDL_Rect *dstrect) { Uint8 r, g, b; int y1,u1,v1; int y,x; int height = src->h < dstrect->h ? src->h: dstrect->h; int width = src->w < dstrect->w ? src->w: dstrect->w; int uv_off = 0; Uint32 pixel; if(dst->format != SDL_YV12_OVERLAY)return 1; for(y = 0; y < height; ++y) { for(x = 0; x < width; ++x) { switch(src->format->BitsPerPixel) { case 8: pixel = *((Uint8*)src->pixels + y*src->pitch + x); break; case 16: pixel = *((Uint16*)src->pixels + y*src->pitch/2 + x); break; case 32: pixel = *((Uint32*)src->pixels + y*src->pitch/4 + x); break; default: return -1; } SDL_GetRGB(pixel, src->format, &r, &g, &b); rgb2yuv(r, g, b, &y1, &u1, &v1); memset(dst->pixels[0] + (dstrect->y + y) * dst->pitches[0] + (dstrect->x + x), (Uint8)y1, 1); if((x%2 == 0 ) && (y%2 == 0 )) { memset(dst->pixels[1] + (uv_off + dstrect->y /2) * dst->pitches[1] + (dstrect->x/2 + x/2), (Uint8)v1, 1); memset(dst->pixels[2] + (uv_off + dstrect->y /2) * dst->pitches[2] + (dstrect->x/2 + x/2), (Uint8)u1, 1); } } if(y%2 == 0)++uv_off; } retu