将YUV_420_888转换为JPEG并保存文件，结果导致图像失真。

Question

将YUV_420_888转换为JPEG并保存文件，结果导致图像失真。

14

我在我的git仓库https://github.com/ahasbini/cameraview/tree/camera_preview_imp中使用了提供的ImageUtil类，该类可在此回答https://dev59.com/QFkS5IYBdhLWcg3wSk1G#40152147中找到，来实现帧预览回调。 ImageReader被设置为以ImageFormat.YUV_420_888格式预览帧，然后使用ImageUtil类将其转换为ImageFormat.JPEG并将其发送到帧回调函数。演示应用程序会每50个帧保存一帧回调的图像到文件中。所有保存的帧图像都出现了以下类似的扭曲现象：

如果我已经对Camera2进行以下更改，将ImageReader更改为使用ImageFormat.JPEG：

mPreviewImageReader = ImageReader.newInstance(previewSize.getWidth(),
    previewSize.getHeight(), ImageFormat.JPEG, /* maxImages */ 2);
mCamera.createCaptureSession(Arrays.asList(surface, mPreviewImageReader.getSurface()),
    mSessionCallback, null);

图像没有任何失真，但帧速率显著下降，视图开始滞后。因此，我认为ImageUtil类没有正确转换。

- ahasbini

最终的带有畸变的图像是写入文件中的图像吗？ - Volodymyr Kulyk

我在哪里可以看到 onImageAvailable(ImageReader reader) (ImageReader.OnImageAvailableListener) 方法？ - Volodymyr Kulyk

在 Camera2 类中的 mOnPreviewAvailableListener 变量内。 - ahasbini

请看这里：https://github.com/ahasbini/cameraview/blob/camera_preview_imp/library/src/main/api21/com/google/android/cameraview/Camera2.java#L188 - ahasbini

让我们在聊天中继续这个讨论。 - ahasbini

显示剩余3条评论

4个回答

3

更新了ImageUtil：

public final class ImageUtil {

    public static byte[] NV21toJPEG(byte[] nv21, int width, int height, int quality) {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        YuvImage yuv = new YuvImage(nv21, ImageFormat.NV21, width, height, null);
        yuv.compressToJpeg(new Rect(0, 0, width, height), quality, out);
        return out.toByteArray();
    }

    // nv12: true = NV12, false = NV21
    public static byte[] YUV_420_888toNV(ByteBuffer yBuffer, ByteBuffer uBuffer, ByteBuffer vBuffer, boolean nv12) {
        byte[] nv;

        int ySize = yBuffer.remaining();
        int uSize = uBuffer.remaining();
        int vSize = vBuffer.remaining();

        nv = new byte[ySize + uSize + vSize];

        yBuffer.get(nv, 0, ySize);
        if (nv12) {//U and V are swapped
            vBuffer.get(nv, ySize, vSize);
            uBuffer.get(nv, ySize + vSize, uSize);
        } else {
            uBuffer.get(nv, ySize , uSize);
            vBuffer.get(nv, ySize + uSize, vSize);
        }
        return nv;
    }

    public static byte[] YUV_420_888toI420SemiPlanar(ByteBuffer yBuffer, ByteBuffer uBuffer, ByteBuffer vBuffer,
                                                     int width, int height, boolean deInterleaveUV) {
        byte[] data = YUV_420_888toNV(yBuffer, uBuffer, vBuffer, deInterleaveUV);
        int size = width * height;
        if (deInterleaveUV) {
            byte[] buffer = new byte[3 * width * height / 2];

            // De-interleave U and V
            for (int i = 0; i < size / 4; i += 1) {
                buffer[i] = data[size + 2 * i + 1];
                buffer[size / 4 + i] = data[size + 2 * i];
            }
            System.arraycopy(buffer, 0, data, size, size / 2);
        } else {
            for (int i = size; i < data.length; i += 2) {
                byte b1 = data[i];
                data[i] = data[i + 1];
                data[i + 1] = b1;
            }
        }
        return data;
    }
}

将byte[] data写入文件作为JPEG的操作：

//image.getPlanes()[0].getBuffer(), image.getPlanes()[1].getBuffer()
//image.getPlanes()[2].getBuffer(), image.getWidth(), image.getHeight()
byte[] nv21 = ImageUtil.YUV_420_888toI420SemiPlanar(yBuffer, uBuffer, vBuffer, width, height, false);
byte[] data = ImageUtil.NV21toJPEG(nv21, width, height, 100);
//now write `data` to file

!!!在处理完图片后不要忘记关闭它!!!

image.close();

- Volodymyr Kulyk

更新发布在聊天室中：http://chat.stackoverflow.com/rooms/144450/discussion-between-ahasbini-and-volodymyr-kulyk - ahasbini

0

Java(Android)中将Camera2的YUV_420_888格式转换为Jpeg：

@Override
public void onImageAvailable(ImageReader reader){
    Image image = null;

    try {
        image = reader.acquireLatestImage();
        if (image != null) {

            byte[] nv21;
            ByteBuffer yBuffer = mImage.getPlanes()[0].getBuffer();
            ByteBuffer uBuffer = mImage.getPlanes()[1].getBuffer();
            ByteBuffer vBuffer = mImage.getPlanes()[2].getBuffer();

            int ySize = yBuffer.remaining();
            int uSize = uBuffer.remaining();
            int vSize = vBuffer.remaining();

            nv21 = new byte[ySize + uSize + vSize];

            //U and V are swapped
            yBuffer.get(nv21, 0, ySize);
            vBuffer.get(nv21, ySize, vSize);
            uBuffer.get(nv21, ySize + vSize, uSize);

            String savingFilepath = getYUV2jpg(nv21);



        }
    } catch (Exception e) {
        Log.w(TAG, e.getMessage());
    }finally{
        image.close();// don't forget to close
    }
}

  public String getYUV2jpg(byte[] data) {
    File imageFile = new File("your parent directory", "picture.jpeg");//no i18n
    BufferedOutputStream bos = null;
    try {
        bos = new BufferedOutputStream(new FileOutputStream(imageFile));
        bos.write(data);
        bos.flush();
        bos.close();
    } catch (IOException e) {

        return e.getMessage();
    } finally {
        try {
            if (bos != null) {
                bos.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
    return imageFile.getAbsolutePath();
}

注意：处理图像旋转问题。

- Shyam Kumar

这个不起作用 :( 在此之后，格式仍然不是JPEG。 - Jorge Barraza Z

0

我认为在YUV的NV和YV格式上存在一些混淆。NV（半平面）具有交错的U/V，而YV（平面）则没有。因此，在这里进行的转换是YV12/21而不是NV12/21。

- programmer

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- ahasbini · Accepted Answer

@volodymyr-kulyk提供的解决方案没有考虑图像内平面的行跨度。下面的代码可以解决这个问题（image是android.media.Image类型）:

data = NV21toJPEG(YUV420toNV21(image), image.getWidth(), image.getHeight(), 100);

实现方式如下：

private static byte[] NV21toJPEG(byte[] nv21, int width, int height, int quality) {
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    YuvImage yuv = new YuvImage(nv21, ImageFormat.NV21, width, height, null);
    yuv.compressToJpeg(new Rect(0, 0, width, height), quality, out);
    return out.toByteArray();
}

private static byte[] YUV420toNV21(Image image) {
    Rect crop = image.getCropRect();
    int format = image.getFormat();
    int width = crop.width();
    int height = crop.height();
    Image.Plane[] planes = image.getPlanes();
    byte[] data = new byte[width * height * ImageFormat.getBitsPerPixel(format) / 8];
    byte[] rowData = new byte[planes[0].getRowStride()];

    int channelOffset = 0;
    int outputStride = 1;
    for (int i = 0; i < planes.length; i++) {
        switch (i) {
            case 0:
                channelOffset = 0;
                outputStride = 1;
                break;
            case 1:
                channelOffset = width * height + 1;
                outputStride = 2;
                break;
            case 2:
                channelOffset = width * height;
                outputStride = 2;
                break;
        }

        ByteBuffer buffer = planes[i].getBuffer();
        int rowStride = planes[i].getRowStride();
        int pixelStride = planes[i].getPixelStride();

        int shift = (i == 0) ? 0 : 1;
        int w = width >> shift;
        int h = height >> shift;
        buffer.position(rowStride * (crop.top >> shift) + pixelStride * (crop.left >> shift));
        for (int row = 0; row < h; row++) {
            int length;
            if (pixelStride == 1 && outputStride == 1) {
                length = w;
                buffer.get(data, channelOffset, length);
                channelOffset += length;
            } else {
                length = (w - 1) * pixelStride + 1;
                buffer.get(rowData, 0, length);
                for (int col = 0; col < w; col++) {
                    data[channelOffset] = rowData[col * pixelStride];
                    channelOffset += outputStride;
                }
            }
            if (row < h - 1) {
                buffer.position(buffer.position() + rowStride - length);
            }
        }
    }
    return data;
}

方法来源于以下链接。