C# rotate bitmap 90 degrees
What about this:
private void RotateAndSaveImage(String input, String output)
{
//create an object that we can use to examine an image file
using (Image img = Image.FromFile(input))
{
//rotate the picture by 90 degrees and re-save the picture as a Jpeg
img.RotateFlip(RotateFlipType.Rotate90FlipNone);
img.Save(output, System.Drawing.Imaging.ImageFormat.Jpeg);
}
}
The bug is in your first call to TranslateTransform
:
g.TranslateTransform((float)b.Width / 2, (float)b.Height / 2);
This transform needs to be in the coordinate space of returnBitmap
rather than b
, so this should be:
g.TranslateTransform((float)b.Height / 2, (float)b.Width / 2);
or equivalently
g.TranslateTransform((float)returnBitmap.Width / 2, (float)returnBitmap.Height / 2);
Your second TranslateTransform
is correct, because it will be applied before the rotation.
However you're probably better off with the simpler RotateFlip
method, as Rubens Farias suggested.
I came across and with a little modification I got it to work. I found some other examples and noticed something missing that made the difference for me. I had to call SetResolution, if I didn't the image ended up the wrong size. I also noticed the Height and Width were backwards, although I think there would be some modification for a non square image anyway. I figured I would post this for anyone who comes across this like I did with the same problem.
Here is my code
private static void RotateAndSaveImage(string input, string output, int angle)
{
//Open the source image and create the bitmap for the rotatated image
using (Bitmap sourceImage = new Bitmap(input))
using (Bitmap rotateImage = new Bitmap(sourceImage.Width, sourceImage.Height))
{
//Set the resolution for the rotation image
rotateImage.SetResolution(sourceImage.HorizontalResolution, sourceImage.VerticalResolution);
//Create a graphics object
using (Graphics gdi = Graphics.FromImage(rotateImage))
{
//Rotate the image
gdi.TranslateTransform((float)sourceImage.Width / 2, (float)sourceImage.Height / 2);
gdi.RotateTransform(angle);
gdi.TranslateTransform(-(float)sourceImage.Width / 2, -(float)sourceImage.Height / 2);
gdi.DrawImage(sourceImage, new System.Drawing.Point(0, 0));
}
//Save to a file
rotateImage.Save(output);
}
}