Bitmap Rotation According to Mouse Position?

Question

Hi,
I am working on a 2d computer graphics project, and I need a good function to rotate a Bitmap 360 degree according to my mouse position.
for example: 

Answer 1

Hi,
I am working on a 2d computer graphics project, and I need a good function to rotate a Bitmap 360 degree according to my mouse position.
for example: 
Hello,
To rotate that image, we need to deal with the following tips.
1. The image size.
If the area for that image rotated is not big enough, it will just lose some parts of that image.
Here is a nice code shared in this thread
http://stackoverflow.com/questions/5199205/how-do-i-rotate-image-then-move-to-the-top-left-0-0-without-cutting-off-the-imag/5200280#5200280.
private Bitmap RotateImage(Bitmap b, float Angle)
// The original bitmap needs to be drawn onto a new bitmap which will probably be bigger
// because the corners of the original will move outside the original rectangle.
// An easy way (OK slightly 'brute force') is to calculate the new bounding box is to calculate the positions of the
// corners after rotation and get the difference between the maximum and minimum x and y coordinates.
float wOver2 = b.Width / 2.0f;
float hOver2 = b.Height / 2.0f;
float radians = -(float)(Angle / 180.0 * Math.PI);
// Get the coordinates of the corners, taking the origin to be the centre of the bitmap.
PointF[] corners = new PointF[]{
new PointF(-wOver2, -hOver2),
new PointF(+wOver2, -hOver2),
new PointF(+wOver2, +hOver2),
new PointF(-wOver2, +hOver2)
for (int i = 0; i < 4; i++)
PointF p = corners[i];
PointF newP = new PointF((float)(p.X * Math.Cos(radians) - p.Y * Math.Sin(radians)), (float)(p.X * Math.Sin(radians) + p.Y * Math.Cos(radians)));
corners[i] = newP;
// Find the min and max x and y coordinates.
float minX = corners[0].X;
float maxX = minX;
float minY = corners[0].Y;
float maxY = minY;
for (int i = 1; i < 4; i++)
PointF p = corners[i];
minX = Math.Min(minX, p.X);
maxX = Math.Max(maxX, p.X);
minY = Math.Min(minY, p.Y);
maxY = Math.Max(maxY, p.Y);
// Get the size of the new bitmap.
SizeF newSize = new SizeF(maxX - minX, maxY - minY);
// ...and create it.
Bitmap returnBitmap = new Bitmap((int)Math.Ceiling(newSize.Width), (int)Math.Ceiling(newSize.Height));
// Now draw the old bitmap on it.
using (Graphics g = Graphics.FromImage(returnBitmap))
g.TranslateTransform(newSize.Width / 2.0f, newSize.Height / 2.0f);
g.RotateTransform(Angle);
g.TranslateTransform(-b.Width / 2.0f, -b.Height / 2.0f);
g.DrawImage(b, 0, 0);
return returnBitmap;
2. The location of that control which displays that image.
If we use a picturebox, and set its sizemode to autosize like the following line, then if you just want to rotate that image to show, and you don't want to that affects the original image, then we need to keep its center point.
this.pictureBox1.SizeMode = PictureBoxSizeMode.AutoSize;
We could add resize event handler after we set image for that picturebox.
        Point pOrign;
        Size sOrign;private void Form1_Load(object sender, EventArgs e)
this.pictureBox1.SizeMode = PictureBoxSizeMode.AutoSize;
Image img = Image.FromFile(@"D:\Documents\New folder\New folder\TestImage.PNG");
this.pictureBox1.Image = img;
this.pictureBox1.InitialImage = img;
pOrign = new Point(this.pictureBox1.Left , this.pictureBox1.Top );
sOrign = new Size(this.pictureBox1.Width, this.pictureBox1.Height);
this.pictureBox1.BorderStyle = BorderStyle.FixedSingle;
this.pictureBox1.Resize += pictureBox1_Resize;
private void pictureBox1_Resize(object sender, EventArgs e)
this.pictureBox1.Left = this.pOrign.X + (this.sOrign.Width - this.pictureBox1.Width) / 2;
this.pictureBox1.Top = this.pOrign.Y + (this.sOrign.Height - this.pictureBox1.Height) / 2;
3. The angle between that center point and your mouse postion.
We could get that value inside the picturebox's container's mouse_move event.
Double angleNew ; private void pictureBoxContainer_MouseMove(object sender, MouseEventArgs e)
angleNew = Math.Atan2(this.pOrign.Y + this.sOrign.Height / 2 - e.Y, this.pOrign.X + this.sOrign.Width/2 - e.X) * 180.0 / Math.PI;
But when to start rotate that image, it should be your chooice, and you could decide when rotate that image with the following line.
this.pictureBox1.Image = (Image)RotateImage(new Bitmap(this.pictureBox1.InitialImage), (float)angleNew);
If you just want to save that change to that image, then you could save that bitmap to file directly.
Happy new year.
Regards.
Carl
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