相机的预览图像被拉伸

Question

I have an Android app that opens the camera, starts preview and streams it on screen. Important note: there is no real SurfaceView associated with the camera. There's only a dummy SurfaceTexture :

m_previewTexture = new SurfaceTexture(58346);
camera.setPreviewTexture(m_previewTexture);

Now, I'm getting the image using the Camera.PreviewCallback . It is irrelevant what I'm doing with it further. So far I'm displaying it on the screen, but I might as well be saving it on the memory card.

Now, the problem. I set preview size to 320x240. I get the image of 320x240 size, all seems fine. But as soon as real life objects come into the frame, I can clearly see that the image is stretched.
My activity's orientation is locked, it doesn't rotate. As I rotate the device relative to a fixed object, I can very clearly see and confirm that the image is stretched. Why could this be and how to avoid stretching?

Answer 1

Does your screen aspect ratio correspond to your preview's frame ratio? Assure correct aspect ratio in onMeasure:

@Override
protected void onMeasure(int widthSpec, int heightSpec) {
    if (this.mAspectRatio == 0) {
        super.onMeasure(widthSpec, heightSpec);
        return;
    }
    int previewWidth = MeasureSpec.getSize(widthSpec);
    int previewHeight = MeasureSpec.getSize(heightSpec);

    int hPadding = getPaddingLeft() + getPaddingRight();
    int vPadding = getPaddingTop() + getPaddingBottom();

    previewWidth -= hPadding;
    previewHeight -= vPadding;

    boolean widthLonger = previewWidth > previewHeight;
    int longSide = (widthLonger ? previewWidth : previewHeight);
    int shortSide = (widthLonger ? previewHeight : previewWidth);
    if (longSide > shortSide * mAspectRatio) {
        longSide = (int) ((double) shortSide * mAspectRatio);
    } else {
        shortSide = (int) ((double) longSide / mAspectRatio);
    }
    if (widthLonger) {
        previewWidth = longSide;
        previewHeight = shortSide;
    } else {
        previewWidth = shortSide;
        previewHeight = longSide;
    }

    // Add the padding of the border.
    previewWidth += hPadding;
    previewHeight += vPadding;

    // Ask children to follow the new preview dimension.
    super.onMeasure(MeasureSpec.makeMeasureSpec(previewWidth, MeasureSpec.EXACTLY),
            MeasureSpec.makeMeasureSpec(previewHeight, MeasureSpec.EXACTLY));
}

from this project