Windows Phone实用开发技巧(32):照片角度处理

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

posted @ 2011-12-18 20:07 Alexis 阅读(...) 评论(...) 编辑 收藏