从IOS图片上传到.net app：旋转

Question

我有以下代码用于将图片从 IOS 设备上传和调整大小到我的 .net 应用程序。用户习惯于纵向拍照，然后所有图片都以错误的旋转方式显示在我的应用程序中。有什么建议可以解决这个问题吗？

            string fileName = Server.HtmlEncode(FileUploadFormbilde.FileName);
            string extension = System.IO.Path.GetExtension(fileName);
            System.Drawing.Image image_file = System.Drawing.Image.FromStream(FileUploadFormbilde.PostedFile.InputStream);
            int image_height = image_file.Height;
            int image_width = image_file.Width;
            int max_height = 300;
            int max_width = 300;

            image_height = (image_height * max_width) / image_width;
            image_width = max_width;

            if (image_height > max_height)
            {
                image_width = (image_width * max_height) / image_height;
                image_height = max_height;
            }

            Bitmap bitmap_file = new Bitmap(image_file, image_width, image_height);
            System.IO.MemoryStream stream = new System.IO.MemoryStream();

            bitmap_file.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
            stream.Position = 0;

            byte[] data = new byte[stream.Length + 1];
            stream.Read(data, 0, data.Length);

Answer 1

您必须从Image.PropertyItems 集合中的EXIF 数据中读取图像的方向值，并进行相应的旋转。

Answer 2

我的朋友，你去吧：

Image originalImage = Image.FromStream(data);

 if (originalImage.PropertyIdList.Contains(0x0112))
        {
            int rotationValue = originalImage.GetPropertyItem(0x0112).Value[0];
            switch (rotationValue)
            {
                case 1: // landscape, do nothing
                    break;

                case 8: // rotated 90 right
                    // de-rotate:
                    originalImage.RotateFlip(rotateFlipType: RotateFlipType.Rotate270FlipNone);
                    break;

                case 3: // bottoms up
                    originalImage.RotateFlip(rotateFlipType: RotateFlipType.Rotate180FlipNone);
                    break;

                case 6: // rotated 90 left
                    originalImage.RotateFlip(rotateFlipType: RotateFlipType.Rotate90FlipNone);
                    break;
            }
        }

Answer 3

这是发布在 Here 的一个更好的解决方案答案他编写了一个简单的帮助类来完成所有这些：

you can check the full source code here.

    private System.Drawing.Image ResizeAndDraw(System.Drawing.Image objTempImage)
        {
          // call image helper to fix the orientation issue 
            var temp = ImageHelper.RotateImageByExifOrientationData(objTempImage, true);
            Size objSize = new Size(150, 200);
            Bitmap objBmp;
            objBmp = new Bitmap(objSize.Width, objSize.Height);

            Graphics g = Graphics.FromImage(objBmp);
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.PixelOffsetMode = PixelOffsetMode.HighQuality;
            //Rectangle rect = new Rectangle(x, y, thumbSize.Width, thumbSize.Height);
            Rectangle rect = new Rectangle(0,0,150,200);
            //g.DrawImage(objTempImage, rect, 0, 0, objTempImage.Width, objTempImage.Height, GraphicsUnit.Pixel);
            g.DrawImage(objTempImage, rect);
            return objBmp;
        }


using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;

public static class ImageHelper
{
    /// <summary>
    /// Rotate the given image file according to Exif Orientation data
    /// </summary>
    /// <param name="sourceFilePath">path of source file</param>
    /// <param name="targetFilePath">path of target file</param>
    /// <param name="targetFormat">target format</param>
    /// <param name="updateExifData">set it to TRUE to update image Exif data after rotation (default is TRUE)</param>
    /// <returns>The RotateFlipType value corresponding to the applied rotation. If no rotation occurred, RotateFlipType.RotateNoneFlipNone will be returned.</returns>
    public static RotateFlipType RotateImageByExifOrientationData(string sourceFilePath, string targetFilePath, ImageFormat targetFormat, bool updateExifData = true)
    {
        // Rotate the image according to EXIF data
        var bmp = new Bitmap(sourceFilePath);
        RotateFlipType fType = RotateImageByExifOrientationData(bmp, updateExifData);
        if (fType != RotateFlipType.RotateNoneFlipNone)
        {
            bmp.Save(targetFilePath, targetFormat);
        }
        return fType;
    }

    /// <summary>
    /// Rotate the given bitmap according to Exif Orientation data
    /// </summary>
    /// <param name="img">source image</param>
    /// <param name="updateExifData">set it to TRUE to update image Exif data after rotation (default is TRUE)</param>
    /// <returns>The RotateFlipType value corresponding to the applied rotation. If no rotation occurred, RotateFlipType.RotateNoneFlipNone will be returned.</returns>
    public static RotateFlipType RotateImageByExifOrientationData(Image img, bool updateExifData = true)
    {
        int orientationId = 0x0112;
        var fType = RotateFlipType.RotateNoneFlipNone;
        if (img.PropertyIdList.Contains(orientationId))
        {
            var pItem = img.GetPropertyItem(orientationId);
            fType = GetRotateFlipTypeByExifOrientationData(pItem.Value[0]);
            if (fType != RotateFlipType.RotateNoneFlipNone)
            {
                img.RotateFlip(fType);
                // Remove Exif orientation tag (if requested)
                if (updateExifData) img.RemovePropertyItem(orientationId);
            }
        }
        return fType;
    }

    /// <summary>
    /// Return the proper System.Drawing.RotateFlipType according to given orientation EXIF metadata
    /// </summary>
    /// <param name="orientation">Exif "Orientation"</param>
    /// <returns>the corresponding System.Drawing.RotateFlipType enum value</returns>
    public static RotateFlipType GetRotateFlipTypeByExifOrientationData(int orientation)
    {
        switch (orientation)
        {
            case 1:
            default:
                return RotateFlipType.RotateNoneFlipNone;
            case 2:
                return RotateFlipType.RotateNoneFlipX;
            case 3:
                return RotateFlipType.Rotate180FlipNone;
            case 4:
                return RotateFlipType.Rotate180FlipX;
            case 5:
                return RotateFlipType.Rotate90FlipX;
            case 6:
                return RotateFlipType.Rotate90FlipNone;
            case 7:
                return RotateFlipType.Rotate270FlipX;
            case 8:
                return RotateFlipType.Rotate270FlipNone;
        }
    }
}