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

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;

 

 

In the above code I have provided comments for better understanding.

 

So I think now we can crop any image easily with the help of this scenario.