data byte array size different for onPictureTaken

问题:

Why is the data byte array size different for onPictureTaken(byte[] data, Camera camera) and onPreviewFrame(byte[] data, Camera camera). The former has the original image and hence gives me a clean image and the latter gives me a pixelated image. I am not using onPictureTaken because it does not get triggered sometimes. If my picture size is 1600 x 1400 and screen size is 800 x 480 onPictureTaken gives me 1600 x 1400 and onPreviewFrame gives me 800 x 480

This is my code:

mCamera.setOneShotPreviewCallback(new Camera.PreviewCallback() {
            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {
                Camera.Parameters parameters = camera.getParameters();
                int format = parameters.getPreviewFormat();
                //YUV formats require more conversion
                if (format == ImageFormat.NV21 || format == ImageFormat.YUY2 || format == ImageFormat.NV16) {
                    int w = parameters.getPreviewSize().width;
                    int h = parameters.getPreviewSize().height;
                    // Get the YuV image
                    YuvImage yuv_image = new YuvImage(data, format, w, h, null);
}

I have been stuck with this issue for one week.

P.S. - In case of negative ratings please state the reason

回答1:

Why is the data byte array size different for onPictureTaken(byte[] data, Camera camera) and onPreviewFrame(byte[] data, Camera camera).

Because they are different images with different resolutions in different encodings. It would be a minor miracle if they were the same size.

The former has the original image and hence gives me a clean image and the latter gives me a pixelated image

Preview frames are generally of lower quality, because they need to be captured at a high rate of speed.

I am not using onPictureTaken because it does not get triggered sometimes

While I have encountered many problems with the camera APIs, that is not one of them.

onPreviewFrame gives me 800 x 480

You specify the preview resolution in setPreviewSize() on Camera.Parameters.