How To Make Image Editor Tool In C# - Cropping Image

Hirendra Sisodiya
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ImageEditorInCSharp.zip

Updated 8/29/2018 - Formatted

My last two articles discussed how to load an image in a Windows form and how to resize that image; see this:

Part 1: Open an image

Part 2: Resizing image

Now we will discuss how to crop an image.

Design form like this view

In the crop tab there are two buttons; one is "Make selection" and the other is "Ok".

For cropping an image we will need to define a region to crop; in this article we will use a rectangle for defining such an area or region.

We can click the "MakeSelection" button and then draw a rectangle on the PictureBox with the help of the mouse.

Code for draw rectangle

Declare some private variables for locating the cursor and defining drawing objects:

int cropX;
int cropY;
int cropWidth;
int cropHeight;
int oCropX;
int oCropY;
public Pen cropPen;
public DashStyle cropDashStyle = DashStyle.DashDot;

We will use mouse down and mouse move events for doing this. We will need to implement this code for the mouse down event:

if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
Cursor = Cursors.Cross;
cropX = e.X;
cropY = e.Y;
cropPen = new Pen(Color.Black, 1);
cropPen.DashStyle = DashStyle.DashDotDot;
}
PictureBox1.Refresh();

In the above code there are two variables; one is cropX for the x position of the rectangle location and another is cropY for the y position. cropPen is the object of pen class with pensize and pencolor.

And write this code on mouse move event:

if (PictureBox1.Image == null)
return;
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
PictureBox1.Refresh();
cropWidth = e.X - cropX;
cropHeight = e.Y - cropY;
PictureBox1.CreateGraphics().DrawRectangle(cropPen, cropX, cropY, cropWidth, cropHeight);
}

On mouse event we can find the cursor position with the help of event arg e so we can easily determine the rectangle's width and height. And use drawrectangle method. In the above code cropPen determines the color, size and other styles of the rectangle, cropx is the x coordinate of the upper left corner of rectangle, y is the y coordinate of the upper left corner of the rectangle and cropWidth and cropHeight are the width and height of the rectangle respectivly.

Code for crop

Cursor = Cursors.Default;
if (cropWidth < 1)
{
return;
}
Rectangle rect = new Rectangle(cropX, cropY, cropWidth, cropHeight);
//First we define a rectangle with the help of already calculated points
Bitmap OriginalImage = new Bitmap(PictureBox1.Image, PictureBox1.Width, PictureBox1.Height);
//Original image
Bitmap _img = new Bitmap(cropWidth, cropHeight);
// for cropinf image
Graphics g = Graphics.FromImage(_img);
// create graphics
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
//set image attributes
g.DrawImage(OriginalImage, 0, 0, rect, GraphicsUnit.Pixel);
PictureBox1.Image = _img;
PictureBox1.Width = _img.Width;
PictureBox1.Height = _img.Height;
PictureBoxLocation();
btnCrop.Enabled = false;