System.Drawing.Graphics绘制从IOS拍摄的图片时，如何将图片旋转90度？

Question

我有以下代码，用System.Drawing.Graphics将上传的图像绘制在150 x 200 div中，但当图像来自IOS设备时，图片会向右旋转90度。

FYI：我在JavaScript画布中绘制图像时也遇到了同样的问题，此解决方案对我有用。因此，我正在寻找一个C#中等效的解决方案。

     private System.Drawing.Image ResizeAndDraw(System.Drawing.Image objTempImage)
            {
                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;
            }

- Helen Araya

Answer 1

我从这里发布的答案中解决了问题：这里。他编写了一个简单的辅助类来完成所有操作：

你可以在这里查看完整的源代码。

    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;
        }
    }
}

- Helen Araya

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注意：在Linux中，pItem.Value[0]可能与Windows不同。在我的代码中，我使用了RuntimeInformation.IsOSPlatform(OSPlatform.Windows)?pItem.Value[0]: pItem.Value.Last()。 - 我零0七