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目录

前言

插值算法

双线性插值算法

代码示例

前言

相机生成的图像一般是bayer阵列的raw图，这时候如果转换成我们需要的rgb图像，就需要对应的bayer插值算法将丢失的rgb信息通过算法补齐

插值算法

常见的插值算法一般有如下几种

• 
  邻近插值算法
  
• 
  双线性插值算法
  
• 
  高质量线性插值算法
  
• 
  边缘感应算法
  
• VNG算法(这里暂不介绍）
• AHD算法(这里暂不介绍）

双线性插值算法

双线性插值是再bayer转rgb中最常用的方法。由于直接取旁边像素容易使图像马赛克话，因此，双线性插值通过取其相邻像素的平均值来内插每个通道中的遗漏值，比如蓝色通道，缺少了红色和绿色，就以周边的红色和绿色来算平均值，

选取当前需要插值的像素点，以3*3矩阵去分割，缺少的像素就按下图算平均值即可

代码示例

void ClearBorders(uint8_t *rgb, int sx, int sy, int w)
{
    int i, j;
    // black edges are added with a width w:
    i = 3 * sx * w - 1;
    j = 3 * sx * sy - 1;
    while (i >= 0) {
        rgb[i--] = 0;
        rgb[j--] = 0;
    }

    int low = sx * (w - 1) * 3 - 1 + w * 3;
    i = low + sx * (sy - w * 2 + 1) * 3;
    while (i > low) {
        j = 6 * w;
        while (j > 0) {
            rgb[i--] = 0;
            j--;
        }
        i -= (sx - 2 * w) * 3;
    }
}

int bayer_Bilinear(const uint8_t *B2R_RESTRICT bayer, uint8_t *B2R_RESTRICT rgb, int sx, int sy, int tile)
{
    const int bayerStep = sx;
    const int rgbStep = 3 * sx;
    int width = sx;
    int height = sy;
    /*
       the two letters  of the OpenCV name are respectively
       the 4th and 3rd letters from the blinky name,
       and we also have to switch R and B (OpenCV is BGR)

       CV_BayerBG2BGR <-> DC1394_COLOR_FILTER_BGGR
       CV_BayerGB2BGR <-> DC1394_COLOR_FILTER_GBRG
       CV_BayerGR2BGR <-> DC1394_COLOR_FILTER_GRBG

       int blue = tile == CV_BayerBG2BGR || tile == CV_BayerGB2BGR ? -1 : 1;
       int start_with_green = tile == CV_BayerGB2BGR || tile == CV_BayerGR2BGR;
     */
    int blue = tile == DC1394_COLOR_FILTER_BGGR
        || tile == DC1394_COLOR_FILTER_GBRG ? -1 : 1;
    int start_with_green = tile == DC1394_COLOR_FILTER_GBRG
        || tile == DC1394_COLOR_FILTER_GRBG;

    if ((tile>DC1394_COLOR_FILTER_MAX)||(tile<DC1394_COLOR_FILTER_MIN))
        return DC1394_INVALID_COLOR_FILTER;

    ClearBorders(rgb, sx, sy, 1);
    rgb += rgbStep + 3 + 1;
    height -= 2;
    width -= 2;

    for (; height--; bayer += bayerStep, rgb += rgbStep) {
        int t0, t1;
        const uint8_t *bayerEnd = bayer + width;

        if (start_with_green) {
            /* OpenCV has a bug in the next line, which was
               t0 = (bayer[0] + bayer[bayerStep * 2] + 1) >> 1; */
            t0 = (bayer[1] + bayer[bayerStep * 2 + 1] + 1) >> 1;
            t1 = (bayer[bayerStep] + bayer[bayerStep + 2] + 1) >> 1;
            rgb[-blue] = (uint8_t) t0;
            rgb[0] = bayer[bayerStep + 1];
            rgb[blue] = (uint8_t) t1;
            bayer++;
            rgb += 3;
        }

        if (blue > 0) {
            for (; bayer <= bayerEnd - 2; bayer += 2, rgb += 6) {
                t0 = (bayer[0] + bayer[2] + bayer[bayerStep * 2] +
                      bayer[bayerStep * 2 + 2] + 2) >> 2;
                t1 = (bayer[1] + bayer[bayerStep] +
                      bayer[bayerStep + 2] + bayer[bayerStep * 2 + 1] +
                      2) >> 2;
                rgb[-1] = (uint8_t) t0;
                rgb[0] = (uint8_t) t1;
                rgb[1] = bayer[bayerStep + 1];

                t0 = (bayer[2] + bayer[bayerStep * 2 + 2] + 1) >> 1;
                t1 = (bayer[bayerStep + 1] + bayer[bayerStep + 3] +
                      1) >> 1;
                rgb[2] = (uint8_t) t0;
                rgb[3] = bayer[bayerStep + 2];
                rgb[4] = (uint8_t) t1;
            }
        } else {
            for (; bayer <= bayerEnd - 2; bayer += 2, rgb += 6) {
                t0 = (bayer[0] + bayer[2] + bayer[bayerStep * 2] +
                      bayer[bayerStep * 2 + 2] + 2) >> 2;
                t1 = (bayer[1] + bayer[bayerStep] +
                      bayer[bayerStep + 2] + bayer[bayerStep * 2 + 1] +
                      2) >> 2;
                rgb[1] = (uint8_t) t0;
                rgb[0] = (uint8_t) t1;
                rgb[-1] = bayer[bayerStep + 1];

                t0 = (bayer[2] + bayer[bayerStep * 2 + 2] + 1) >> 1;
                t1 = (bayer[bayerStep + 1] + bayer[bayerStep + 3] +
                      1) >> 1;
                rgb[4] = (uint8_t) t0;
                rgb[3] = bayer[bayerStep + 2];
                rgb[2] = (uint8_t) t1;
            }
        }

        if (bayer < bayerEnd) {
            t0 = (bayer[0] + bayer[2] + bayer[bayerStep * 2] +
                  bayer[bayerStep * 2 + 2] + 2) >> 2;
            t1 = (bayer[1] + bayer[bayerStep] +
                  bayer[bayerStep + 2] + bayer[bayerStep * 2 + 1] +
                  2) >> 2;
            rgb[-blue] = (uint8_t) t0;
            rgb[0] = (uint8_t) t1;
            rgb[blue] = bayer[bayerStep + 1];
            bayer++;
            rgb += 3;
        }

        bayer -= width;
        rgb -= width * 3;

        blue = -blue;
        start_with_green = !start_with_green;
    }
    return 0;
}