RGA Rotate

当需要对图片进行旋转时， 也可以使用RGA来实现， 以提高效率。

使用RGA进行旋转时， 对图片的尺寸有要求， w_stride需要16字节对齐， 否则RGA会失败。

此demo通过v4l2读取mipi摄像头(1920x1080 30@fps)， 使用RGA把NV12转换成BGR, 再把缩放成1920x1088（16的倍数）。

1. 环境准备

在使用RGA之前，请确保你的RK3588运行环境已具备以下条件：

• 设备系统里有DMA节点， 如下:

linaro@linaro-alip:~$ ls /dev/dma_heap/system-uncached-dma32 -l  
crw-rw---- 1 root video 251, 3 10月14日 05:55 /dev/dma_heap/system-uncached-dma32

此demo也是基于DMA buffer， 详细请查看RGA DMA.

• RGA库与头文件： SDK中应包含 librga.so 动态库以及对应的头文件（通常是 rga.h 或 RgaApi.h）, Neardi设备出厂固件里已经包含。

2. RGA旋转代码

此demo是把一帧图像旋转90度， 实现代码如下:

inline int ALIGN16(int x) { return (x + 15) & ~15; }  
  
int rga_rotate(int src_fd, int src_size, int dst_fd, int dst_size,  
               int width, int height, int rotation_angle) {  
    const int bpp = 3; // bytes per pixel for BGR888  
  
    if (src_fd < 0 || dst_fd < 0) {  
        cerr << "invalid fd\n";  
        return -1;  
    }  
  
    // compute dst logical dims based on rotation  
    int dst_width = width, dst_height = height;  
    if (rotation_angle == IM_HAL_TRANSFORM_ROT_90 || rotation_angle == IM_HAL_TRANSFORM_ROT_270) {  
        dst_width = height;  
        dst_height = width;  
    }  
  
    // RGA recommended align width to 16 pixels (wstride in pixels)  
    int src_wstride_pix = ALIGN16(width);  
    int dst_wstride_pix = ALIGN16(dst_width);  
  
    // hstride usually is number of lines (height)  
    int src_hstride = height;  
    int dst_hstride = dst_height;  
  
    // compute required buffer sizes in bytes  
    size_t required_src_bytes = size_t(src_wstride_pix) * src_hstride * bpp;  
    size_t required_dst_bytes = size_t(dst_wstride_pix) * dst_hstride * bpp;  
  
    if ((size_t)src_size < required_src_bytes) {  
        cerr << "src buffer too small: " << src_size << " < " << required_src_bytes << endl;  
        return -1;  
    }  
    if ((size_t)dst_size < required_dst_bytes) {  
        cerr << "dst buffer too small: " << dst_size << " < " << required_dst_bytes << endl;  
        return -1;  
    }  
  
    // import dma fds -> rga handles  
    rga_buffer_handle_t src_handle = importbuffer_fd(src_fd, src_size);  
    rga_buffer_handle_t dst_handle = importbuffer_fd(dst_fd, dst_size);  
    if (!src_handle || !dst_handle) {  
        if (src_handle) releasebuffer_handle(src_handle);  
        if (dst_handle) releasebuffer_handle(dst_handle);  
        cerr << "importbuffer_fd failed\n";  
        return -1;  
    }  
  
    // wrap buffer handles  
    rga_buffer_t src = wrapbuffer_handle(src_handle, width, height, RK_FORMAT_BGR_888);  
    rga_buffer_t dst = wrapbuffer_handle(dst_handle, dst_width, dst_height, RK_FORMAT_BGR_888);  
  
    // IMPORTANT: wstride is usually in pixels (aligned),  
    // and when RGA reads memory the real bytes-per-line = wstride * bpp.  
    src.wstride = src_wstride_pix;  
    src.hstride = src_hstride;  
    dst.wstride = dst_wstride_pix;  
    dst.hstride = dst_hstride;  
  
    // check  
    int chk = imcheck(src, dst, {}, {});  
    if (IM_STATUS_NOERROR != chk) {  
        cerr << "imcheck error: " << imStrError((IM_STATUS)chk) << endl;  
        releasebuffer_handle(src_handle);  
        releasebuffer_handle(dst_handle);  
        return -1;  
    }  
  
    /*  
     * Rotate the src image by 90°.  
           src_img          dst_img  
        --------------    -----------  
        |.           |    |        .|  
        |     <      | => |    ^    |  
        |            |    |         |  
        --------------    |         |  
                          -----------  
     */  
    int ret = imrotate(src, dst, rotation_angle);  
    if (ret != IM_STATUS_SUCCESS) {  
        cerr << "imrotate failed: " << imStrError((IM_STATUS)ret) << endl;  
        releasebuffer_handle(src_handle);  
        releasebuffer_handle(dst_handle);  
        return -1;  
    }  
  
    // release handles (dma-buf still valid)  
    releasebuffer_handle(src_handle);  
    releasebuffer_handle(dst_handle);  
  
    return 0;  
}

3. 使用示例

在V4L2-CAMERA基础上， 把上面拷贝代码集成进去。

或者从此处下载完整的代码.

demo程序运行后， 也可以查看RGA的负载， 如下:

root@linaro-alip:/sys/kernel/debug/rkrga# cat load  
num of scheduler = 3  
================= load ==================  
scheduler[0]: rga3  
         load = 18%  
-----------------------------------  
scheduler[1]: rga3  
         load = 0%  
-----------------------------------  
scheduler[2]: rga2  
         load = 0%  
-----------------------------------  
=========================================  
<session>  <status>  <tgid>  <process>  
3          active    5939    ./rga_rotate 22