很容易检测图像方向和替换位图使用:
/**
* Rotate an image if required.
* @param img
* @param selectedImage
* @return
*/
private static Bitmap rotateImageIfRequired(Context context,Bitmap img, Uri selectedImage) {
// Detect rotation
int rotation = getRotation(context, selectedImage);
if (rotation != 0) {
Matrix matrix = new Matrix();
matrix.postRotate(rotation);
Bitmap rotatedImg = Bitmap.createBitmap(img, 0, 0, img.getWidth(), img.getHeight(), matrix, true);
img.recycle();
return rotatedImg;
}
else{
return img;
}
}
/**
* Get the rotation of the last image added.
* @param context
* @param selectedImage
* @return
*/
private static int getRotation(Context context,Uri selectedImage) {
int rotation = 0;
ContentResolver content = context.getContentResolver();
Cursor mediaCursor = content.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
new String[] { "orientation", "date_added" },
null, null, "date_added desc");
if (mediaCursor != null && mediaCursor.getCount() != 0) {
while(mediaCursor.moveToNext()){
rotation = mediaCursor.getInt(0);
break;
}
}
mediaCursor.close();
return rotation;
}
为了避免大图像的内存不足，我建议您使用以下方法重新缩放图像:
private static final int MAX_HEIGHT = 1024;
private static final int MAX_WIDTH = 1024;
public static Bitmap decodeSampledBitmap(Context context, Uri selectedImage)
throws IOException {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
InputStream imageStream = 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);
Bitmap img = BitmapFactory.decodeStream(imageStream, null, options);
img = rotateImageIfRequired(img, selectedImage);
return img;
}
由于Android操作系统的问题，不能使用ExifInterface来获取方向:
https://code.google.com/p/android/issues/detail?id=19268
这里是calculateInSampleSize
/**
* Calculate an inSampleSize for use in a {@link BitmapFactory.Options} object when decoding
* bitmaps using the decode* methods from {@link 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
*/
public static int calculateInSampleSize(BitmapFactory.Options options,
int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
// Calculate ratios of height and width to requested height and width
final int heightRatio = Math.round((float) height / (float) reqHeight);
final int widthRatio = Math.round((float) width / (float) reqWidth);
// 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 = heightRatio < widthRatio ? heightRatio : 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).
final float totalPixels = width * height;
// Anything more than 2x the requested pixels we'll sample down further
final float totalReqPixelsCap = reqWidth * reqHeight * 2;
while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
inSampleSize++;
}
}
return inSampleSize;
}
