问题描述
我使用了
如果我已将 ImageReader 更改为使用 ImageFormat.JPEG 而是通过执行以下更改在 Camera2 ：
mPreviewImageReader = ImageReader.newInstance（previewSize.getWidth（ ），
previewSize.getHeight（），ImageFormat.JPEG，/ * maxImages * / 2）;
mCamera.createCaptureSession（Arrays.asList（surface，mPreviewImageReader.getSurface（）），
mSessionCallback，null）;
图像正常运行而没有任何失真但帧速率显着下降且视图开始滞后。因此我认为 ImageUtil 类没有正确转换。
解决方案由@ volodymyr-kulyk提供的没有考虑图像中平面的行间距。下面的代码是诀窍（图像是 android.media.Image 类型）：
data = NV21toJPEG（YUV420toNV21（image），image.getWidth（），image.getHeight（），100）;
实施：
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）;
返回out.toByteArray（）;
}
private static byte [] YUV420toNV21（图片图片）{
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;
休息;
案例1：
channelOffset = width * height + 1;
outputStride = 2;
休息;
案例2：
channelOffset = width * height;
outputStride = 2;
休息;
}
ByteBuffer buffer = planes [i] .getBuffer（）;
int rowStride = planes [i] .getRowStride（）;
int pixelStride = planes [i] .getPixelStride（）;
int shift =（i == 0）？ 0：1;
int w = width>>转移;
int h = height>>转移;
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）;
}
}
}
返回数据;
}
方法来自以下。
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.
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.
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