在实际项目中,可能需要用户从相册中选择图片然后进行相应的处理。但是不知道大家有没有发现这样一种情况,就是手机里看是竖着的,但是上传到微博或者哪里的时候确实横着的。一种情况是你拿手机竖着拍照得话,照片就是横着的,虽然在手机里看是竖着的。(可能有点抽象,遇到此情况的同学应该深有感触)
那么我们在客户端中应该如何处理这种情况呢?一种想法是获取图片的角度,如果是90°,就把照片翻转过来,再进行相应的操作。那这样就涉及到2个问题
1. 如何获取相册中照片的角度
2. 如何翻转已有的照片(流、或者Bitmap或者WriteableBitmap)
查看了系统的API,并没有对相片的角度提供支持,但是我们可以使用ExifLib开源库去做。
下述的方法就是获取选取图片的角度的
/// <summary> /// get angle of photo /// </summary> /// <param name="stream">photo stream</param> /// <param name="filename">photo name</param> /// <returns>angle of the photo</returns> public static int GetAngle(Stream stream, string filename) {ExifLib.ExifOrientation _orientation;int _angle = 0;stream.Position = 0;JpegInfo info = ExifReader.ReadJpeg(stream, filename);if (info!=null){_orientation = info.Orientation;switch (info.Orientation){case ExifOrientation.TopLeft:case ExifOrientation.Undefined:_angle = 0;break;case ExifOrientation.TopRight:_angle = 90;break;case ExifOrientation.BottomRight:_angle = 180;break;case ExifOrientation.BottomLeft:_angle = 270;break;}}return _angle; }
获取到角度后,如果角度是90°,即是反的,我们需要将其纠正过来,可以使用如下的方法:
private Stream RotateStream(Stream stream, int angle) {stream.Position = 0;if (angle % 90 != 0 || angle < 0) throw new ArgumentException();if (angle % 360 == 0) return stream;BitmapImage bitmap = new BitmapImage();bitmap.SetSource(stream);WriteableBitmap wbSource = new WriteableBitmap(bitmap);WriteableBitmap wbTarget = null;if (angle % 180 == 0){wbTarget = new WriteableBitmap(wbSource.PixelWidth, wbSource.PixelHeight);}else{wbTarget = new WriteableBitmap(wbSource.PixelHeight, wbSource.PixelWidth);}for (int x = 0; x < wbSource.PixelWidth; x++){for (int y = 0; y < wbSource.PixelHeight; y++){switch (angle % 360){case 90:wbTarget.Pixels[(wbSource.PixelHeight - y - 1) + x * wbTarget.PixelWidth] = wbSource.Pixels[x + y * wbSource.PixelWidth];break;case 180:wbTarget.Pixels[(wbSource.PixelWidth - x - 1) + (wbSource.PixelHeight - y - 1) * wbSource.PixelWidth] = wbSource.Pixels[x + y * wbSource.PixelWidth];break;case 270:wbTarget.Pixels[y + (wbSource.PixelWidth - x - 1) * wbTarget.PixelWidth] = wbSource.Pixels[x + y * wbSource.PixelWidth];break;}}}MemoryStream targetStream = new MemoryStream();wbTarget.SaveJpeg(targetStream, wbTarget.PixelWidth, wbTarget.PixelHeight, 0, 100);return targetStream; }
Demo源代码下载
原文Handling picture orientation in CameraCaptureTask in Windows Phone 7