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我正在使用以下帮助程序类来处理相机图像的采样和旋转。

object CaptureImageHelper {

/**
 * This method is responsible for solving the rotation issue if exist. Also scale the images to
 * 1024x1024 resolution
 *
 * @param context       The current context
 * @param selectedImage The Image URI
 * @return Bitmap image results
 * @throws IOException
 */
@Throws(IOException::class)
fun handleSamplingAndRotationBitmap(
    context: Context,
    selectedImage: Uri?,
    isFrontCamera: Boolean
): Bitmap? {
    val MAX_HEIGHT = 1024
    val MAX_WIDTH = 1024

    // First decode with inJustDecodeBounds=true to check dimensions
    val options = BitmapFactory.Options()
    options.inJustDecodeBounds = true
    var imageStream: InputStream = context.getContentResolver().openInputStream(selectedImage!!)!!
    BitmapFactory.decodeStream(imageStream, null, options)
    imageStream.close()

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, MAX_WIDTH, MAX_HEIGHT)

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false
    imageStream = context.getContentResolver().openInputStream(selectedImage!!)!!
    var img = BitmapFactory.decodeStream(imageStream, null, options)
    img = rotateImageIfRequired(img!!, selectedImage, isFrontCamera)
    return img
}

/**
 * Calculate an inSampleSize for use in a [BitmapFactory.Options] object when decoding
 * bitmaps using the decode* methods from [BitmapFactory]. This implementation calculates
 * the closest inSampleSize that will result in the final decoded bitmap having a width and
 * height equal to or larger than the requested width and height. This implementation does not
 * ensure a power of 2 is returned for inSampleSize which can be faster when decoding but
 * results in a larger bitmap which isn't as useful for caching purposes.
 *
 * @param options   An options object with out* params already populated (run through a decode*
 * method with inJustDecodeBounds==true
 * @param reqWidth  The requested width of the resulting bitmap
 * @param reqHeight The requested height of the resulting bitmap
 * @return The value to be used for inSampleSize
 */
private fun calculateInSampleSize(
    options: BitmapFactory.Options,
    reqWidth: Int, reqHeight: Int
): Int {
    // Raw height and width of image
    val height = options.outHeight
    val width = options.outWidth
    var inSampleSize = 1
    if (height > reqHeight || width > reqWidth) {

        // Calculate ratios of height and width to requested height and width
        val heightRatio =
            Math.round(height.toFloat() / reqHeight.toFloat())
        val widthRatio =
            Math.round(width.toFloat() / reqWidth.toFloat())

        // Choose the smallest ratio as inSampleSize value, this will guarantee a final image
        // with both dimensions larger than or equal to the requested height and width.
        inSampleSize = if (heightRatio < widthRatio) heightRatio else widthRatio

        // This offers some additional logic in case the image has a strange
        // aspect ratio. For example, a panorama may have a much larger
        // width than height. In these cases the total pixels might still
        // end up being too large to fit comfortably in memory, so we should
        // be more aggressive with sample down the image (=larger inSampleSize).
        val totalPixels = width * height.toFloat()

        // Anything more than 2x the requested pixels we'll sample down further
        val totalReqPixelsCap = reqWidth * reqHeight * 2.toFloat()
        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++
        }
    }
    return inSampleSize
}

/**
 * Rotate an image if required.
 *
 * @param img           The image bitmap
 * @param selectedImage Image URI
 * @return The resulted Bitmap after manipulation
 */
@Throws(IOException::class)
private fun rotateImageIfRequired(
    img: Bitmap,
    selectedImage: Uri,
    isFrontCamera: Boolean
): Bitmap? {
    val ei = ExifInterface(selectedImage.path!!)
    val orientation: Int =
        ei.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)
    return when (orientation) {
        ExifInterface.ORIENTATION_ROTATE_90 -> rotateImage(img, 90, isFrontCamera)
        ExifInterface.ORIENTATION_ROTATE_180 -> rotateImage(img, 180, isFrontCamera)
        ExifInterface.ORIENTATION_ROTATE_270 -> rotateImage(img, 270, isFrontCamera)
        else -> img
    }
}

private fun rotateImage(
    img: Bitmap,
    degree: Int,
    isFrontCamera: Boolean
): Bitmap? {
    val matrix = Matrix()
    if(isFrontCamera) {
        val matrixMirrorY = Matrix()
        val mirrorY = floatArrayOf(-1f, 0f, 0f, 0f, 1f, 0f, 0f, 0f, 1f)
        matrixMirrorY.setValues(mirrorY)
        matrix.postConcat(matrixMirrorY)
        matrix.preRotate(270f)
    } else {
        matrix.postRotate(degree.toFloat())
    }
    val rotatedImg =
        Bitmap.createBitmap(img, 0, 0, img.width, img.height, matrix, true)
    img.recycle()
    return rotatedImg
}
}

调用助手类

val bitmap = CaptureImageHelper.handleSamplingAndRotationBitmap(requireContext(), Uri.fromFile(cameraImage!!), false)

我得到的问题是随机的。大多数情况下，如果我得到以下语句的旋转图像

ei.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)

返回 ExifInterface.ORIENTATION_ROTATE_90 这很好，代码可以正确旋转该图像。但有时图像被旋转，但 Exif getAttributeInt 返回 ExifInterface.ORIENTATION_NORMAL。我相信这意味着没有针对此图像的 Exif/Orientation 数据，它返回默认值。

退出获取属性方法

    public int getAttributeInt(@NonNull String tag, int defaultValue) {
    if (tag == null) {
        throw new NullPointerException("tag shouldn't be null");
    }
    ExifAttribute exifAttribute = getExifAttribute(tag);
    if (exifAttribute == null) {
        return defaultValue;
    }

    try {
        return exifAttribute.getIntValue(mExifByteOrder);
    } catch (NumberFormatException e) {
        return defaultValue;
    }
}
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