Android: Jpeg saved from camera looks corrupted

问题

I'm writing an Android application that saves a JPEG snapshot from the camera when the user clicks a button. Unfortunately, when I look at the JPEG file my code is saving looks corrupted. It appears to be caused by my call to parameters.setPreviewSize (see code snippet below) - if I remove that then the image saves fine; however without it I can't set the preview size and setDisplayOrientation also appears to have no effect without it.

My app is targeting API Level 8 (Android 2.2), and I'm debugging on an HTC Desire HD. Not quite sure what I'm doing wrong here... any help would be very much appreciated!

Cheers, Scottie

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
    // Now that the size is known, set up the camera parameters and begin
    // the preview.
    Camera.Parameters parameters = mCamera.getParameters();        
    Camera.Size size = getBestPreviewSize(w,h);

    // This next call is required in order for preview size to be set and
    // setDisplayOrientation to take effect...
    // Unfortunately it's also causing JPEG to be created wrong
    parameters.setPreviewSize(size.width, size.height);

    parameters.setPictureFormat(ImageFormat.JPEG);
    mCamera.setParameters(parameters);
    mCamera.setDisplayOrientation(90);

    mCamera.startPreview();

}

// This is the snapshot button event handler
public void onSnapshotButtonClick(View target) {
    //void android.hardware.Camera.takePicture(ShutterCallback shutter, 
    //                              PictureCallback raw, PictureCallback jpeg)
    mPreview.mCamera.takePicture(null, null, mPictureCallback);
}


// This saves the camera snapshot as a JPEG file on the SD card
Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
    public void onPictureTaken(byte[] imageData, Camera c) {

        if (imageData != null) {
            FileOutputStream outStream = null;
            try {
                String myJpgPath = String.format(
                        "/sdcard/%d.jpg", System.currentTimeMillis());

                outStream = new FileOutputStream(myJpgPath);
                outStream.write(imageData);
                outStream.close();
                Log.d("TestApp", "onPictureTaken - wrote bytes: "
                        + imageData.length);

                c.startPreview();
                Toast.makeText(getApplicationContext(), String.format("%s written", myJpgPath), Toast.LENGTH_SHORT).show();

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
            }
        }
    }
};

回答1:

Another workaround is to match the aspect ratio between preview and picture sizes (i.e. setPreviewSize(w1,h1); setPictureSize(w2,h2) with w1/h1 ~ w2/h2 (small differences seem to be ok)). E.g. for Desire HD S w1=800,h1=480, w2=2592,h2=1552 works as well as w1=960,h1=720,h2=2592,h2=1952 (if you don't mind distorted images ;-)

回答2:

I assume that you are using a common implementation of the getBestPreviewSize(w,h) method that is floating about, where you cycle through the different getSupportedPreviewSizes() to find the best match. Although I am not certain as to why it causes the images to be distorted, I have found that calling the parameters.setPreviewSize(size.width, size.height) method with the output of the getBestPreviewSize method is what is causing the problem on the HTC Desire. I have also verified that by commenting it out, the distorted image issue goes away.

来源：https://stackoverflow.com/questions/5859876/android-jpeg-saved-from-camera-looks-corrupted