问题
I've used the ImageUtil class provided in https://stackoverflow.com/a/40152147/2949966 within my git repo: https://github.com/ahasbini/cameraview/tree/camera_preview_imp (note the implementation is in camera_preview_imp branch) to implement a frame preview callback. An ImageReader is set to preview frames in the ImageFormat.YUV_420_888 format which will be converted into ImageFormat.JPEG using the ImageUtil class and send it to the frame callback. The demo app saves a frame from the callback to a file every 50 frames. All of the saved frame images are coming out distorted similar to below:
If I've changed the ImageReader to use ImageFormat.JPEG instead by doing the following changes in Camera2:
mPreviewImageReader = ImageReader.newInstance(previewSize.getWidth(),
previewSize.getHeight(), ImageFormat.JPEG, /* maxImages */ 2);
mCamera.createCaptureSession(Arrays.asList(surface, mPreviewImageReader.getSurface()),
mSessionCallback, null);
the image is coming properly without any distortions however the frame rate drops significantly and the view starts to lag. Hence I believe the ImageUtil class is not converting properly.
回答1:
Solution provided by @volodymyr-kulyk does not take into consideration the row stride of the planes within the image. Below code does the trick (image is of android.media.Image type):
data = NV21toJPEG(YUV420toNV21(image), image.getWidth(), image.getHeight(), 100);
And the implementations:
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;
}
Method was gotten from the following link.
回答2:
Updated 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;
}
}
Operations to write in file byte[] data as JPEG:
//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
!!! do not forget to close image after processing !!!
image.close();
回答3:
Camera2 YUV_420_888 to Jpeg in Java(Android):
@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();
}
Note: Handle the image rotation issue.
来源：https://stackoverflow.com/questions/44022062/converting-yuv-420-888-to-jpeg-and-saving-file-results-distorted-image