c# - How can I rotate an image by any degree?

Question

I have animated gif and I'm using a class to parse the images(frames) from it. The class is:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Collections.Generic;
using System.IO;

public class AnimatedGif
{
    private List<AnimatedGifFrame> mImages = new List<AnimatedGifFrame>();
    public AnimatedGif(string path)
    {
        Image img = Image.FromFile(path);
        int frames = img.GetFrameCount(FrameDimension.Time);
        if (frames <= 1) throw new ArgumentException("Image not animated");
        byte[] times = img.GetPropertyItem(0x5100).Value;
        int frame = 0;
        for (; ; )
        {
            int dur = BitConverter.ToInt32(times, 4 * frame);
            mImages.Add(new AnimatedGifFrame(new Bitmap(img), dur));
            if (++frame >= frames) break;
            img.SelectActiveFrame(FrameDimension.Time, frame);
        }
        img.Dispose();
    }
    public List<AnimatedGifFrame> Images { get { return mImages; } }
}

public class AnimatedGifFrame
{
    private int mDuration;
    private Image mImage;
    internal AnimatedGifFrame(Image img, int duration)
    {
        mImage = img; mDuration = duration;
    }
    public Image Image { get { return mImage; } }
    public int Duration { get { return mDuration; } }
}

Now in form1 I loop over the frames in this case 4 and I want to rotate the animation by any degree. Now its rotating each 45 or 90 degrees. I want to add more frames(images) to the animation so if I set the rotation to 31 or to 10 degrees so I will see the animation rotating in 10 degrees.

This is the code in Form1 which is not working good. I'm using a function for the rotation which I didn't test yet if its any working.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace AnimatedGifEditor
{
    public partial class Form1 : Form
    {
        Image myImage;
        AnimatedGif myGif;
        Bitmap bitmap;

        public Form1()
        {
            InitializeComponent();

            myImage = Image.FromFile(@"D:fananimation.gif");
            myGif = new AnimatedGif(@"D:fananimation.gif");
            for (int i = 0; i < myGif.Images.Count; i++)
            {
                pictureBox1.Image = myGif.Images[3].Image;
                bitmap = new Bitmap(pictureBox1.Image);
                rotateImage(bitmap, 76);
                pictureBox1.Image = bitmap;
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

private Bitmap RotateImg(Bitmap bmp, float angle, Color bkColor)
    {
        int w = bmp.Width;
        int h = bmp.Height;
        bmp.PixelFormat pf = default(bmp.PixelFormat);
        if (bkColor == Color.Transparent)
        {
            pf = bmp.Format32bppArgb;
        }
        else
        {
            pf = bmp.PixelFormat;
        }

        Bitmap tempImg = new Bitmap(w, h, pf);
        Graphics g = Graphics.FromImage(tempImg);
        g.Clear(bkColor);
        g.DrawImageUnscaled(bmp, 1, 1);
        g.Dispose();

        GraphicsPath path = new GraphicsPath();
        path.AddRectangle(new RectangleF(0f, 0f, w, h));
        Matrix mtrx = new Matrix();
        //Using System.Drawing.Drawing2D.Matrix class 
        mtrx.Rotate(angle);
        RectangleF rct = path.GetBounds(mtrx);
        Bitmap newImg = new Bitmap(Convert.ToInt32(rct.Width), Convert.ToInt32(rct.Height), pf);
        g = Graphics.FromImage(newImg);
        g.Clear(bkColor);
        g.TranslateTransform(-rct.X, -rct.Y);
        g.RotateTransform(angle);
        g.InterpolationMode = InterpolationMode.HighQualityBilinear;
        g.DrawImageUnscaled(tempImg, 0, 0);
        g.Dispose();
        tempImg.Dispose();
        return newImg;
    }
    }
}

The animated gif I'm using for the test can be found here:

Answer 1

I didn't understand what's your problem but I think that your code could be improved. I think that you don't need to use directly the Matrix class. There are some functions that does this work for you. Infact the only things you need are: set the point of the rotation as the center, rotate the graphics and draw on it, using some functions by the Graphics class. So to rotate an image you can use this simple code:

private Bitmap RotateImage(Bitmap bmp, float angle) {
     Bitmap rotatedImage = new Bitmap(bmp.Width, bmp.Height);
     rotatedImage.SetResolution(bmp.HorizontalResolution, bmp.VerticalResolution);

     using (Graphics g = Graphics.FromImage(rotatedImage)) {
        // Set the rotation point to the center in the matrix
        g.TranslateTransform(bmp.Width / 2, bmp.Height / 2);
        // Rotate
        g.RotateTransform(angle);
        // Restore rotation point in the matrix
        g.TranslateTransform(- bmp.Width / 2, - bmp.Height / 2);
        // Draw the image on the bitmap
        g.DrawImage(bmp, new Point(0, 0));
     }

     return rotatedImage;
}