Develop Reference

Image doesn't cover the whole PictureBox

I'm creating an image viewer using C# and having a small issue with scaling (zooming) PictureBox.
I have a PictureBox inside a Panel, and I can zoom (scale) an image using the controls at the top left and using mouse wheel just fine. However, at some specific zoom scales, the image doesn't cover the whole PictureBox.
For example, SO logo (100x116 pixels) at 100% and at 200%:
Image at the right is 199x131 pixels, while the PictureBox is 200x132.
I've set the BackColor of the PictureBox to Red to make the issue noticeable.
This doesn't always happen, just at specific zoom levels. Why is that? Am I doing something wrong?
I can set the BackColor of PictureBox to the BackColor of the Panel to give the illusion that the image covers the whole PictureBox, but I rather fix the problem. If I can't, I'll apply the tricky solution.
Relevant code:
float zoom = 1;
Image image = null;
public MainForm(string[] args)
{
InitializeComponent();
image = ImageBox.Image;
this.ImageBox.MouseWheel += ImageBox_MouseWheel;
if (args.Length > 0)
{
LoadImage(args[0]);
}
}
private void ImageBox_Paint(object sender, PaintEventArgs e)
{
// disable interpolation (sharper pixels)
e.Graphics.InterpolationMode = InterpolationMode.NearestNeighbor;
// https://msdn.microsoft.com/en-us/library/ms142046(v=vs.110).aspx
e.Graphics.DrawImage(image,
new Rectangle(0, 0, ImageBox.Width, ImageBox.Height),
0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
}
private void LoadImage(string path)
{
image = Image.FromFile(path);
ImageBox.Width = (int)(image.Width * zoom);
ImageBox.Height = (int)(image.Height * zoom);
ImageBox.Image = image;
CenterImage();
}
private void ScaleImage()
{
ImageBox.Image = null;
ImageBox.Width = (int)(image.Width * zoom);
ImageBox.Height = (int)(image.Height * zoom);
ImageBox.Image = image;
CenterImage();
}
I've also created a repository, in case anyone wants to examine the app live.

You need to adjust the rectangle in ImageBox_Paint. Try this:
private void ImageBox_Paint(object sender, PaintEventArgs e)
{
int add = ImageBox.Width / 200;
// disable interpolation (sharper pixels)
e.Graphics.InterpolationMode = InterpolationMode.NearestNeighbor;
// https://msdn.microsoft.com/en-us/library/ms142046(v=vs.110).aspx
e.Graphics.DrawImage(image,
new Rectangle(0, 0, ImageBox.Width + add, ImageBox.Height + add),
0, 0, image.Width, image.Height, GraphicsUnit.Pixel);
}

Simply set the SizeMode property of the PictureBox to Zoom. Then adapting the size of the picturebox will automatically make the image stretch to its full size.
You don't even need that Paint event listener; it's inbuilt functionality. Just change the dimensions of the PictureBox to the calculated zoomed dimensions of the image and you're done.

Erase Part of Bitmap with another Bitmap

Let me preface this with a real life product; You may remember in Elementary school, they had scratch paper which basically consisted of a rainbow-colored sheet of paper with a black film on top. You would take a sharp object and peel away the black film to expose the colored paper.
I am attempting to do the same thing using images in a picture box.
My idea consists of these things:
A textured image.
A black rectangle the size of the picture box.
A circle image.
What I am trying to achieve is to open a program, have an image drawn to a picture box with the black rectangle on top of it. Upon clicking the picture box it uses the circle to invert the alpha of the rectangle where I click using the circle as a reference.
My Problem-
I cannot figure out any way to erase (set the transparency of) a part of the black rectangle where I click.
For the life of me, I do not know of any method to cut a window in an image. It is almost like a reverse crop, where I keep the exterior elements rather than the interior, exposing the textured image below.
Can WinForms not do this? Am I crazy? Should I just give up?
I should mention that I prefer not to have to change alpha on a pixel per pixel basis. It would slow the program down far too much to be used as a pseudo-painter. If that is the only way, however, feel free to show.
Here is an image of what I'm trying to achieve:

This is not really hard:
Set the colored image as a PictureBox's BackgroundImage.
Set a black image as its Image.
And draw into the image using the normal mouse events and a transparent Pen..
We need a point list to use DrawCurve:
List<Point> currentLine = new List<Point>();
We need to prepare and clear the the black layer:
private void ClearSheet()
{
if (pictureBox1.Image != null) pictureBox1.Image.Dispose();
Bitmap bmp = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.ClientSize.Height);
using (Graphics G = Graphics.FromImage(bmp)) G.Clear(Color.Black);
pictureBox1.Image = bmp;
currentLine.Clear();
}
private void cb_clear_Click(object sender, EventArgs e)
{
ClearSheet();
}
To draw into the Image we need to use an associated Graphics object..:
void drawIntoImage()
{
using (Graphics G = Graphics.FromImage(pictureBox1.Image))
{
// we want the tranparency to copy over the black pixels
G.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
G.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
G.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
using (Pen somePen = new Pen(Color.Transparent, penWidth))
{
somePen.MiterLimit = penWidth / 2;
somePen.EndCap = System.Drawing.Drawing2D.LineCap.Round;
somePen.LineJoin = System.Drawing.Drawing2D.LineJoin.Round;
somePen.StartCap = System.Drawing.Drawing2D.LineCap.Round;
if (currentLine.Count > 1)
G.DrawCurve(somePen, currentLine.ToArray());
}
}
// enforce the display:
pictureBox1.Image = pictureBox1.Image;
}
The usual mouse events:
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
currentLine.Add(e.Location);
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
currentLine.Add(e.Location);
drawIntoImage();
}
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
currentLine.Clear();
}
That's all that's needed. Make sure to keep the PB's SizeMode = Normal or else the pixels won't match..!
Note that there are a few challenges when you want to get soft edges, more painting tools, letting a simple click paint a dot or an undo or other finer details to work. But the basics are not hard at all..
Btw, changing Alpha is not any different from changing the color channels.
As an alternative you may want to play with a TextureBrush:
TextureBrush brush = new TextureBrush(pictureBox1.BackgroundImage);
using (Pen somePen = new Pen(brush) )
{
// basically
// the same drawing code..
}
But I found this to be rather slow.
Update:
Using a png-file as a custom tip is a little harder; the main reason is that the drawing is reversed: We don't want to draw the pixels, we want to clear them. GDI+ doesn't support any such composition modes, so we need to do it in code.
To be fast we use two tricks: LockBits will be as fast as it gets and restricting the area to our custom brush tip will prevent wasting time.
Let's assume you have a file to use and load it into a bitmap:
string stampFile = #"yourStampFile.png";
Bitmap stamp = null;
private void Form1_Load(object sender, EventArgs e)
{
stamp = (Bitmap) Bitmap.FromFile(stampFile);
}
Now we need a new function to draw it into our Image; instead of DrawCurve we need to use DrawImage:
void stampIntoImage(Point pt)
{
Point point = new Point(pt.X - stamp.Width / 2, pt.Y - stamp.Height / 2);
using (Bitmap stamped = new Bitmap(stamp.Width, stamp.Height) )
{
using (Graphics G = Graphics.FromImage(stamped))
{
stamp.SetResolution(stamped.HorizontalResolution, stamped.VerticalResolution);
G.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver;
G.DrawImage(pictureBox1.Image, 0, 0,
new Rectangle(point, stamped.Size), GraphicsUnit.Pixel);
writeAlpha(stamped, stamp);
}
using (Graphics G = Graphics.FromImage(pictureBox1.Image))
{
G.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
G.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
G.CompositingQuality =
System.Drawing.Drawing2D.CompositingQuality.HighQuality;
G.DrawImage(stamped, point);
}
}
pictureBox1.Image = pictureBox1.Image;
}
A few notes: I found that I hat to do an explicit SetResolution since the stamp file I photoshopped was 72dpi and the default Bitmaps in my program were 120dpi. Watch out for these differences!
I start the Bitmap to be drawn by copying the right part of the current Image.
Then I call a fast routine that applies the alpha of the stamp to it:
void writeAlpha(Bitmap target, Bitmap source)
{
// this method assumes the bitmaps both are 32bpp and have the same size
int Bpp = 4;
var bmpData0 = target.LockBits(
new Rectangle(0, 0, target.Width, target.Height),
ImageLockMode.ReadWrite, target.PixelFormat);
var bmpData1 = source.LockBits(
new Rectangle(0, 0, source.Width, source.Height),
ImageLockMode.ReadOnly, source.PixelFormat);
int len = bmpData0.Height * bmpData0.Stride;
byte[] data0 = new byte[len];
byte[] data1 = new byte[len];
Marshal.Copy(bmpData0.Scan0, data0, 0, len);
Marshal.Copy(bmpData1.Scan0, data1, 0, len);
for (int i = 0; i < len; i += Bpp)
{
int tgtA = data0[i+3]; // opacity
int srcA = 255 - data1[i+3]; // transparency
if (srcA > 0) data0[i + 3] = (byte)(tgtA < srcA ? 0 : tgtA - srcA);
}
Marshal.Copy(data0, 0, bmpData0.Scan0, len);
target.UnlockBits(bmpData0);
source.UnlockBits(bmpData1);
}
I use a simple rule: Reduce target opacity by the source transparency and make sure we don't get negative.. You may want to play around with it.
Now all we need is to adapt the MouseMove; for my tests I have added two RadioButtons to switch between the original round pen and the custom stamp tip:
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == System.Windows.Forms.MouseButtons.Left)
{
if (rb_pen.Checked)
{
currentLine.Add(e.Location);
drawIntoImage();
}
else if (rb_stamp.Checked) { stampIntoImage(e.Location); };
}
}
I didn't use a fish but you can see the soft edges:
Update 2: Here is a MouseDown that allows for simple clicks:
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (rb_pen.Checked) currentLine.Add(e.Location);
else if (rb_stamp.Checked)
{
{ stampIntoImage(e.Location); };
}
}

How to Draw on Zoomable Image in C# windows Forms

so am implementing a project that can read image pan it, zoom it and do other stuff.. everything was going well until i tried implementing a draw with right mouse button.
the problem is when i draw a line, the line that appears on the image does not correspond to the line i drew on screen, meaning its shifted and i know its because of the re-sizing and zooming of the image, but when i draw lines on the image with its original size(the image) and with panning also ; i have no problem.
here's the code.
so first here is how i load the image when i click browse and select image
Myimage = new Bitmap(ImagePath);
resized = myImage.Size;
imageResize();
pictureBox.Paint += new System.Windows.Forms.PaintEventHandler(this.pictureBox_Paint);
pictureBox.Invalidate();
the imageResize function does the following:
void imageResize()
{
//calculated the size to fit the control i will draw the image on
resized.Height = someMath;
resized.Width = someMath;
}
then in the event handler for the pictureBox_Paint event i wrote:
private void pictureBox_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
// Create a local version of the graphics object for the PictureBox.
Graphics PboxGraphics = e.Graphics;
PboxGraphics.DrawImage(myImage, imageULcorner.X, imageULcorner.Y, resized.Width, resized.Height);
}
as you can see the resized size is not the original image size i did this because i wanted the image to show on the picturebox control centralized and filled now the next part IS WHERE MY PROBLEM BEGINS
i have to draw lines on image using right mouse button so i implemented pictureBox_MouseDown & pictureBox_MouseUp event handlers
// mouse down event handler
private void pictureBox_MouseDown(object sender, MouseEventArgs e)
{
else if (mouse.Button == MouseButtons.Right)
{
mouseDown = mouse.Location;
mouseDown.X = mouseDown.X - imageULcorner.X;
mouseDown.Y = mouseDown.Y - imageULcorner.Y;
draw = true;
}
}
here is the mouse up event handler
//Mouse UP
private void pictureBox_MouseUp(object sender, MouseEventArgs e)
{
else if (mouse.Button == MouseButtons.Right)
{
if (draw)
{
mouseLocationNow.X = mouse.X - imageULcorner.X;
mouseLocationNow.Y = mouse.Y - imageULcorner.Y;
//
// get graphics object of the image ( the original not the resized)
// as the resized image only appears when i draw on the graphics of the
// pictureBox control
// i know the problem lies here but how can i fix it
//
Graphics image = Graphics.FromImage(myImage);
Pen pen = new Pen(Color.Red, 2);
image.DrawLine(pen, mouseLocationNow, mouseDown);
pictureBox.Invalidate();
}
draw = false;
}
so in the end i want to be able to draw on the re-sized image and make it correspond to the real image and also to the screen where i draw the line
thanks and sorry for the long post but this problem has been driving me crazy.

Here is a PictureBox subclass that supports the ability to apply zooming not only to the Image but also to graphics you draw onto its surface.
It includes a SetZoom function to zoom in by scaling both itself and a Matrix.
It also has a ScalePoint function you can use to calculate the unscaled coordinates from the pixel coordinates you receive in the mouse events.
The idea is to use a Transformation Matrix to scale any pixels the Graphics object will draw in the Paint event.
I include a little code for the form for testing.
public partial class ScaledPictureBox : PictureBox
{
public Matrix ScaleM { get; set; }
float Zoom { get; set; }
Size ImgSize { get; set; }
public ScaledPictureBox()
{
InitializeComponent();
ScaleM = new Matrix();
SizeMode = PictureBoxSizeMode.Zoom;
}
public void InitImage()
{
if (Image != null)
{
ImgSize = Image.Size;
Size = ImgSize;
SetZoom(100);
}
}
public void SetZoom(float zoomfactor)
{
if (zoomfactor <= 0) throw new Exception("Zoom must be positive");
float oldZoom = Zoom;
Zoom = zoomfactor / 100f;
ScaleM.Reset();
ScaleM.Scale(Zoom , Zoom );
if (ImgSize != Size.Empty) Size = new Size((int)(ImgSize.Width * Zoom),
(int)(ImgSize.Height * Zoom));
}
public PointF ScalePoint(PointF pt)
{ return new PointF(pt.X / Zoom , pt.Y / Zoom ); }
}
Here is the code in the Form that does the testing:
public List<PointF> somePoints = new List<PointF>();
private void scaledPictureBox1_MouseClick(object sender, MouseEventArgs e)
{
somePoints.Add(scaledPictureBox1.ScalePoint(e.Location) );
scaledPictureBox1.Invalidate();
}
private void scaledPictureBox1_Paint(object sender, PaintEventArgs e)
{
// here we apply the scaling matrix to the graphics object:
e.Graphics.MultiplyTransform(scaledPictureBox1.ScaleM);
using (Pen pen = new Pen(Color.Red, 10f))
{
PointF center = new PointF(scaledPictureBox1.Width / 2f,
scaledPictureBox1.Height / 2f);
center = scaledPictureBox1.ScalePoint(center);
foreach (PointF pt in somePoints)
{
DrawPoint(e.Graphics, pt, pen);
e.Graphics.DrawLine(Pens.Yellow, center, pt);
}
}
}
public void DrawPoint(Graphics G, PointF pt, Pen pen)
{
using (SolidBrush brush = new SolidBrush(pen.Color))
{
float pw = pen.Width;
float pr = pw / 2f;
G.FillEllipse(brush, new RectangleF(pt.X - pr, pt.Y - pr, pw, pw));
}
}
Here are the results after drawing a few points showing the same points in four different zoom settings; the ScaledPictureBox is obviously placed in an AutoScroll-Panel. The lines show how to use the regular drawing commands..

Crop image using a fixed-size draggable picturebox

I'm working on a winforms project that involves cropping an image. My goal is to do this by using a fixed-size draggable picturebox control, allowing the user to select the area they want to preserve.
My problem is when I crop the image; it "works", but the crop area offsets a little. Here's the result I get:
To clarify, I'm not talking about the zooming, that's per design. Notice the orange box is mostly focusing on the eye of the storm, but the cropped image is not.
This is my code for the crop operation:
private void tsbRecortar_Click(object sender, EventArgs e)
{
Rectangle recorte = new Rectangle(pbxSeleccion.Location.X, pbxSeleccion.Location.Y, pbxSeleccion.Width, pbxSeleccion.Height);
foto = recortarImagen(foto, recorte);
pbxImagen.Image = foto;
}
private Image recortarImagen(Image imagen, Rectangle recuadro)
{
try
{
Bitmap bitmap = new Bitmap(imagen);
Bitmap cropedBitmap = bitmap.Clone(recuadro, bitmap.PixelFormat);
return (Image)(cropedBitmap);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "Error");
return null;
}
}
pbxSeleccion is the draggable orange rectangle; its parent is pbxImage (I re-parent it on form's load).
As you can see, I'm using the coordinates of pbxSeleccion to define the starting point of the crop area, but is not working as expected... sometimes, I even get an "Out of Memory" exception.
I think this has to do with how the image loads in the parent picturebox, something about how the margin is handled "under the hood", but nothing I tried fixes it... just changes the magnitude of the offset.
Searching the web and SO has helped me a lot, but for this particular issue, I can't seem to find an answer... please, feel free to point out improvements to my code, I haven't been coding for long and I'm new to C# and .NET
Any help is highly appreciated. Cheers!

Suppose your original image is displayed in a PictureBox. You passed in the wrong location of the orange cropping window. Here is the corrected code for you:
private void tsbRecortar_Click(object sender, EventArgs e){
Point p = yourPictureBox.PointToClient(pbxSelection.PointToScreen(Point.Empty));
Rectangle recorte = new Rectangle(p.X, p.Y, pbxSeleccion.Width, pbxSeleccion.Height);
foto = recortarImagen(foto, recorte);
pbxImagen.Image = foto;
}
I use PointToClient and PointToScreen here because I think it's the best way to do. You can then change the container of your pictureBox safely without having to modify the code. If you use the code like the following, it's not dynamically enough when you want to place your pictureBox in another container:
Rectangle recorte = new Rectangle(pbxSeleccion.X + yourPictureBox.Left,
pbxSeleccion.Y + yourPictureBox.Top,
pbxSeleccion.Width, pbxSeleccion.Height);
NOTE: you can also use RectangleToClient and RectangleToScreen like this:
private void tsbRecortar_Click(object sender, EventArgs e){
Rectangle recorte = yourPictureBox.RectangleToClient(pbxSeleccion.RectangleToScreen(pbxSeleccion.ClientRectangle));
foto = recortarImagen(foto, recorte);
pbxImagen.Image = foto;
}

Try This Code for Cropping the Image in picturebox
public static Image Fit2PictureBox(this Image image, PictureBox picBox)
{
Bitmap bmp = null;
Graphics g;
// Scale:
double scaleY = (double)image.Width / picBox.Width;
double scaleX = (double)image.Height / picBox.Height;
double scale = scaleY < scaleX ? scaleX : scaleY;
// Create new bitmap:
bmp = new Bitmap(
(int)((double)image.Width / scale),
(int)((double)image.Height / scale));
// Set resolution of the new image:
bmp.SetResolution(
image.HorizontalResolution,
image.VerticalResolution);
// Create graphics:
g = Graphics.FromImage(bmp);
// Set interpolation mode:
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
// Draw the new image:
g.DrawImage(
image,
new Rectangle( // Ziel
0, 0,
bmp.Width, bmp.Height),
new Rectangle( // Quelle
0, 0,
image.Width, image.Height),
GraphicsUnit.Pixel);
// Release the resources of the graphics:
g.Dispose();
// Release the resources of the origin image:
image.Dispose();
return bmp;
}
public static Image Crop(this Image image, Rectangle selection)
{
Bitmap bmp = image as Bitmap;
// Check if it is a bitmap:
if (bmp == null)
throw new ArgumentException("Kein gültiges Bild (Bitmap)");
// Crop the image:
Bitmap cropBmp = bmp.Clone(selection, bmp.PixelFormat);
// Release the resources:
image.Dispose();
return cropBmp;
}
Write The Following Code For Mouse Event on PictureBox
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
_selecting = true;
_selection = new Rectangle(new Point(e.X, e.Y), new Size());
}
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left && _selecting)
{
// Create cropped image:
try
{
Image img = pictureBox1.Image.Crop(_selection);
// Fit image to the picturebox:
pictureBox1.Image = img.Fit2PictureBox(pictureBox1);
}
catch { }
_selecting = false;
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
// Update the actual size of the selection:
if (_selecting)
{
_selection.Width = e.X - _selection.X;
_selection.Height = e.Y - _selection.Y;
// Redraw the picturebox:
pictureBox1.Refresh();
}
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
if (_selecting)
{
// Draw a rectangle displaying the current selection
Pen pen = Pens.LightSkyBlue;
e.Graphics.DrawRectangle(pen, _selection);
}
}
Output Screen
Before Cropping
After Cropping

C# : GDI+ Image cropping

I have an image .I want to crop 10 px from left and 10px from right of the image.I used the below code to do so
string oldImagePath="D:\\RD\\dotnet\\Images\\photo1.jpg";
Bitmap myOriginalImage = (Bitmap)Bitmap.FromFile(oldImagePath);
int newWidth = myOriginalImage.Width;
int newHeight = myOriginalImage.Height;
Rectangle cropArea = new Rectangle(10,0, newWidth-10, newHeight);
Bitmap target = new Bitmap(cropArea.Width, cropArea.Height);
using (Graphics g = Graphics.FromImage(target))
{
g.DrawImage(myOriginalImage,cropArea);
}
target.Save("D:\\RD\\dotnet\\Images\\test.jpg");
But this is not giving me the results which i expect. This outputs an image which has 10 px cropped from the right and a resized image.Instead of cropiing it is resizing the width i think.So the image is shrinked(by width). Can any one correct me ? Thanks in advance

Your new width should be reduced by twice the crop margin, since you'll be chopping off that amount from both sides.
Next, when drawing the image into the new one, draw it at a negative offset. This causes the area that you aren't interested in to be clipped off.
int cropX = 10;
Bitmap target = new Bitmap(myOriginalImage.Width - 2*cropX, myOriginalImage.Height);
using (Graphics g = Graphics.FromImage(target))
{
g.DrawImage(myOriginalImage, -cropX, 0);
}

My guess is this line
Rectangle cropArea = new Rectangle(10,0, newWidth-10, newHeight);
should be
Rectangle cropArea = new Rectangle(10,0, newWidth-20, newHeight);
Set the width of the new rectangle to be 20 less than the original - 10 for each side.
Some indication what result it is giving you would be helpful in confirming this.

Corey Ross is correct. Alternately, you can translate along the negative x axis and render at 0.0, 0.0. Should produce identical results.
using (Graphics g = Graphics.FromImage(target))
{
g.TranslateTransform(-cropX, 0.0f);
g.DrawImage(myOriginalImage, 0.0f, 0.0f);
}

You need to use the overload that has you specify both Destination Rectangle, and Source Rectangle.
Below is an interactive form of this using a picture box on a form. It allows you to drag the image around. I suggest making the picture box 100 x 100 and have a much larger image such as a full screen window you've captured with alt-prtscr.
class Form1 : Form
{
// ...
Image i = new Bitmap(#"C:\Users\jasond\Pictures\foo.bmp");
Point lastLocation = Point.Empty;
Size delta = Size.Empty;
Point drawLocation = Point.Empty;
bool dragging = false;
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
if (!dragging)
{
lastLocation = e.Location;
dragging = true;
}
delta = new Size(lastLocation.X - e.Location.X, lastLocation.Y - e.Location.Y);
lastLocation = e.Location;
if (!delta.IsEmpty)
{
drawLocation.X += delta.Width;
drawLocation.Y += delta.Height;
pictureBox1.Invalidate();
}
}
else
{
dragging = false;
}
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
Rectangle source = new Rectangle(drawLocation,pictureBox1.ClientRectangle.Size);
e.Graphics.DrawImage(i,pictureBox1.ClientRectangle,source, GraphicsUnit.Pixel);
}
//...

Okay, I totally fail at explaining this, but hang on:
The DrawImage function requires the location of the image, as well as it's position. You need a second position for cropping as how the old relates to the new, not vice versa.
That was entirely incomprehensible, but here is the code.
g.DrawImage(myOriginalImage, -cropArea.X, -cropArea.Y);
I hope that explains it more then I did.