How to crop image using mouse selection in picturebox in windows form

Question

0.00/5 (No votes)

See more:

Cropping image is wrong. Where I'm wrong?

C#

        int cropX;
        int cropY;
        int cropWidth;
        int cropHeight;
        public Pen cropPen;

        public DashStyle cropDashStyle = DashStyle.DashDot;
        public bool Makeselection = false;

<pre>private void button4_Click(object sender, EventArgs e)
        {
            Makeselection = true;
            button4.Enabled = true;

            Cursor = Cursors.Default;

            try
            {
                if (cropWidth < 1)
                {
                    return;
                }
                Rectangle rect = new Rectangle(cropX, cropY, cropWidth, cropHeight);
                Bitmap OriginalImage = new Bitmap(pictureBox1.Image, pictureBox1.Width, pictureBox1.Height);
                Bitmap _img = new Bitmap(cropWidth, cropHeight);
                Graphics g = Graphics.FromImage(_img);

                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                g.DrawImage(OriginalImage, 0, 0, rect, GraphicsUnit.Pixel);

                pictureBox1.Image = _img;
                pictureBox1.Width = _img.Width;
                pictureBox1.Height = _img.Height;
            }
            catch (Exception ex)
            {

            }
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
         
                Cursor = Cursors.Default;
                if (Makeselection)
                {

                    try
                    {
                        if (e.Button == System.Windows.Forms.MouseButtons.Left)
                        {
                            Cursor = Cursors.Cross;
                            cropX = e.X;
                            cropY = e.Y;

                            cropPen = new Pen(Color.Red, 1);
                            cropPen.DashStyle = DashStyle.DashDotDot;


                        }                       
                        pictureBox1.Refresh();
                    }
                    catch (Exception ex)
                    {

                    }
                }
            
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (Makeselection)
            {
                Cursor = Cursors.Default;
            }
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
                Cursor = Cursors.Default;
                if (Makeselection)
                {

                    try
                    {
                        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);
                        }



                    }
                    catch (Exception ex)
                    {
                        //if (ex.Number == 5)
                        //    return;
                    }
                }
            
        }

What I have tried:

Cropping image is wrong. Where I'm wrong?

Posted 27-Feb-19 12:17pm

bartall

Updated 27-Feb-19 21:48pm

Add a Solution

Comments

Patrice T 27-Feb-19 18:47pm

Elaborate "Cropping image is wrong"

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Answer 1 · 2019-02-27T21:49:00

Probably, it's scaling. Check your PictureBox settings, specifically the PictureBox.SizeMode Property (System.Windows.Forms) | Microsoft Docs[^] - if it isn't set to "Normal" then the mouse coordinates you are using are relative to the Picturebox but not the the image it contains. If the image is scaled at all, then when you use mouse coordinates at all they don't match the actual picture you are clipping from.

A couple of other things:
1) Graphics contexts are scarce resources - and you are responsible for Disposing of them when you create them. If you don't, you will get "out of memory" errors long before the GC gets called in to tidy up after you. A using block is the best way, as it automatically Disposes when the object goes out of scope, regardless of how it exits the block.

C#

using (Graphics g = Graphics.FromImage(_img))
   {
   g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
   ...
   }

2) Why are you creating so many bitmaps? You don't need half of them!
3) Never swallow exceptions:

catch (Exception ex)
{

}

When you do that, you throw away all information that might help you fix a problem later, as well as "hiding" the problem so you don't even know it happened, and can't fix it early enough to not make a proper mess. Log 'em, Show 'em to the user, display them on the Debug console - whatever works for you. But don;t just blanket swallow them!