使用平面4：2：0 YUV全比例像素格式将图像从字节数组转换为位图

Question

Update: I contacted the vendor of the device and they let me know it is using the planar 4:2:0 YUV full scale pixel format. Upon researching I found out there seem to be 3 major formats for YUV 4:2:0 : I420, J420 and YV12. I was excited because there were constants for this image format in the android YuvImage class, when running my code however I got the the following exception:

java.lang.IllegalArgumentException: only support ImageFormat.NV21 and ImageFormat.YUY2 for now

Well thats a bummer..

After that I learned about the differences between YUV420 and NV21:

I tried to write some simple function to interleave the 2 chroma planes like shown in the NV21 pixel format image.

 public static void convertYUY420ToNV21(byte[] data_yuv420, byte[] data_yuv_N21) {
    int idx = (int) (data_yuv_N21.length * (2.0f / 3.0f));
    int j = idx;
    int chroma_plane_end = (int) (idx + ((data_yuv_N21.length - idx) / 2));

    for (int i = idx; i < chroma_plane_end; i++) {
        data_yuv_N21[j] = data_yuv420[i];
        j += 2;
    }
    j = idx + 1;
    for (int i = chroma_plane_end; i < data_yuv_N21.length; i++) {
        data_yuv_N21[j] = data_yuv420[i];
        j += 2;
    }

However, the result seems still the same as from my original code.. One possible reason I was thinking about was the size of the byte array (1843200). I read that for YUV420 the depth of one pixel is 12bit. The camera resolution is 1280x720 which are 921,600 pixels or 1,382,400 bytes. That is one third less than the actual byte array size. I read there might be some padding between the planes but I'm stuck on how to find out about that.

The YuvImage class has a strides parameter in its constructor but I'm not sure how to use even after reading the android developer documentation.

Any clues?

Original Post:

I'm having the following problem: I'm trying to access the camera of a device where there is no information provided on what type of camera or image format is used. The only information provided is on how to retrieve a byte array containing the video stream output. I found out however that the resolution is 1280x720 and the byte array size is 1843200. By googling I stumbled across cameras with the exact same size and dimensions using YUYV and similar pixel formats. Based on that knowledge I wrote the code below:

ByteArrayOutputStream out = new ByteArrayOutputStream();
            YuvImage yuv = new YuvImage(data, ImageFormat.YUY2, 1280, 720, null);
            yuv.compressToJpeg(new Rect(0, 0, 1280, 720), 100, out);
            byte[] bytes = out.toByteArray();
            bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            if (bitmap != null) {
                ImageView cameraImageView = (ImageView) findViewById(R.id.imageView);
                cameraImageView.setImageBitmap(bitmap);
            } 

The BitmapFactory.decodeByteArray function returned a valid bitmap but when displaying it I saw the image having a green tint and purple spots, probably something related to the color channels? Sample Image:

Is there a way how to find out the exact pixel format/ encoding that has been used? I'm not sure what other things to try from here on out. Any advice is appreciated, thanks!

Answer 1

try this :

    /** 
     * Save YUV image data (NV21 or YUV420sp) as JPEG to a FileOutputStream.
     */
    public static boolean saveYUYToJPEG(byte[] imageData,File saveTo,int format,int quality,int width,int height,int rotation,boolean flipHorizontally){
      FileOutputStream fileOutputStream=null;
      YuvImage yuvImg=null;
      try {
        fileOutputStream=new FileOutputStream(saveTo);
        yuvImg=new YuvImage(imageData,format,width,height,null);
        ByteArrayOutputStream jpegOutput=new ByteArrayOutputStream(imageData.length);
        yuvImg.compressToJpeg(new Rect(0,0,width - 1,height - 1),90,jpegOutput);
        Bitmap yuvBitmap=BitmapFactory.decodeByteArray(jpegOutput.toByteArray(),0,jpegOutput.size());
        Matrix imageMatrix=new Matrix();
        if (rotation != 0) {
          imageMatrix.postRotate(rotation);
        }
        if (flipHorizontally) {
        }
        yuvBitmap=Bitmap.createBitmap(yuvBitmap,0,0,yuvBitmap.getWidth(),yuvBitmap.getHeight(),imageMatrix,true);
        yuvBitmap.compress(CompressFormat.JPEG,quality,fileOutputStream);
      }
     catch (  FileNotFoundException e) {
        return false;
      }
      return true;
    }