rgb_to_yuv.c

#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define rgbtoy(b, g, r, y)						\
    y=(unsigned char)(((int)(30*r) + (int)(59*g) + (int)(11*b))/100)

#define rgbtoyuv(b, g, r, y, u, v)					\
    rgbtoy(b, g, r, y);							\
u=(unsigned char)(((int)(-17*r) - (int)(33*g) + (int)(50*b)+12800)/100); \
v=(unsigned char)(((int)(50*r) - (int)(42*g) - (int)(8*b)+12800)/100)


inline int RGBToU(unsigned char r, unsigned char g, unsigned char b)
{
    return ((-38 * r -  74 * g + 112 * b + 128) >> 8) + 128;
}

inline int RGBToV(unsigned char r, unsigned char g, unsigned char b)
{
    return ((112 * r -  94 * g -  18 * b + 128) >> 8) + 128;
}

void RGBToUVRow(const unsigned char* src_rgb0, int src_stride_rgb,
        unsigned char* dst_u, unsigned char* dst_v, int width)
{
    const unsigned char* src_rgb1 = src_rgb0 + src_stride_rgb;
    int x = 0;
    for (; x < width - 1; x += 2) {
        unsigned char ab = (src_rgb0[0] + src_rgb0[3] + src_rgb1[0] + src_rgb1[3]) >> 2;
        unsigned char ag = (src_rgb0[1] + src_rgb0[4] + src_rgb1[1] + src_rgb1[4]) >> 2;
        unsigned char ar = (src_rgb0[2] + src_rgb0[5] + src_rgb1[2] + src_rgb1[5]) >> 2;
        dst_u[0] = RGBToU(ar, ag, ab);
        dst_v[0] = RGBToV(ar, ag, ab);
        src_rgb0 += 6;
        src_rgb1 += 6;
        dst_u += 1;
        dst_v += 1;
    }
}

inline int RGBToY(unsigned char r, unsigned char g, unsigned char b)
{
    return (( 66 * r + 129 * g +  25 * b + 128) >> 8) + 16;
}

void RGBToYRow(const unsigned char* src_argb0, unsigned char* dst_y, int width)
{
    int x = 0;
    for (; x < width; ++x) {
        dst_y[0] = RGBToY(src_argb0[2], src_argb0[1], src_argb0[0]);
        src_argb0 += 3;
        dst_y += 1;
    }
}   

void RGB24ToI420(const unsigned char* src_rgb, int src_stride_rgb24,
        unsigned char* dst_y, int dst_stride_y,
        unsigned char* dst_u, int dst_stride_u,
        unsigned char* dst_v, int dst_stride_v,
        int width, int height)
{
    if (height < 0) {
        height = -height;
        src_rgb = src_rgb + (height - 1) * src_stride_rgb24;
        src_stride_rgb24 = -src_stride_rgb24;
    }
    int y = 0;
    for (; y < height - 1; y += 2) {
        RGBToUVRow(src_rgb, src_stride_rgb24, dst_u, dst_v, width);
        RGBToYRow(src_rgb, dst_y, width);
        RGBToYRow(src_rgb + src_stride_rgb24, dst_y + dst_stride_y, width);
        src_rgb += src_stride_rgb24 * 2;
        dst_y += dst_stride_y * 2;
        dst_u += dst_stride_u;
        dst_v += dst_stride_v;
    }
}