Develop Reference

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); };
}
}

C# Linking point on form

Greeting!
I've been working on a project where you got a form where the user asks for a certain amount of dot (between 1 and 10). Then it draws them on a picturebox with a buttonclick action and then the user could click on any dot and a line between them is drawn.
So far it looks like this:
private void button1_Click(object sender, EventArgs e)
{
pictureBox1.CreateGraphics().Clear(this.BackColor);
Random r = new Random();
int db = new int();
Graphics rl = pictureBox1.CreateGraphics();
db = Convert.ToInt32(textBox1.Text);
if (db > 0 && db < 11)
{
for (int i = 0; i < db; i++)
{
rl.FillRectangle(new SolidBrush(Color.Black), r.Next(4, pictureBox1.Width - 4), r.Next(4, pictureBox1.Height - 4), 5, 5);
}
}
else
{
MessageBox.Show("Wrong number!");
}
}
This only draws the point on the form and i want to make them linkable. My idea is that i put it on a bitmap then i check the x,y coordinates and if the color is black (which means there is a point) I store in dot1 and dot2 and then simply make a drawline command like this:
private bool first = false;
private void Picturebox_Mouse(object sender, MouseEventArgs e)
{
Bitmap bm = new Bitmap(pictureBox1.Image);
Color color = bm.GetPixel(e.X, e.Y);
if (color == Color.Black & first==false)
{
dot1.X = e.X;
dot1.Y = e.Y;
first = true;
}
if (color == Color.Black & first == true)
{
dot2.X = e.X;
dot2.Y = e.X;
first = false;
}
rl.DrawLine(new Pen(Color.Black), dot1, dot2);
}
My question is that is my approach fine or i should do a different way? Also if this can work how do i put the content of the picturebox into a bitmap? I tried to drawing the point into the bitmap diractly then setting the pictureboxs image to the bitmap:
pictureBox1.DrawToBitmap(bm, new Rectangle(r.Next(0, pictureBox1.Width - 4), r.Next(0, pictureBox1.Height - 4), 5, 5));
pictureBox1.BackgroundImage = bm;
and also i tried to reverse it so putting the content to the bitmap:
Bitmap bm = new Bitmap(pictureBox1.Image);
but it doesn't seem to work. So can i get some ideas how to do it?
Any Kind of Idea is Appriciated!Thanks you.

I have done something similar, but as I was doing it on a web page I used an ImageButton instead of a PictureBox, so my code doesn't do exactly what you need, unfortunately. However, to use a bitmap with your image, you can do something like this:
Bitmap flag = new Bitmap(200, 100);
using(Graphics flagGraphics = Graphics.FromImage(flag))
{
// draw something on flagGraphics
pictureBox1.Image = flag;
}
(I actually based this on https://msdn.microsoft.com/en-us/library/ms404307(v=vs.110).aspx)
Note, you will need to change your test for black to something like if(color.ToArgb() == Color.Black.ToArgb()) or it won't work. Also you are setting a Y to an X value when I think it should be a Y!

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

boundaries cut the image when rotated

I want to rotate an image in the picture box. Here is my code.
public static Bitmap RotateImage(Image image, PointF offset, float angle)
{
if (image == null)
{
throw new ArgumentNullException("image");
}
var rotatedBmp = new Bitmap(image.Width, image.Height);
rotatedBmp.SetResolution(image.HorizontalResolution, image.VerticalResolution);
var g = Graphics.FromImage(rotatedBmp);
g.TranslateTransform(offset.X, offset.Y);
g.RotateTransform(angle);
g.TranslateTransform(-offset.X, -offset.Y);
g.DrawImage(image, new PointF(0, 0));
return rotatedBmp;
}
private void button1_Click(object sender, EventArgs e)
{
Image image = new Bitmap(pictureBox1.Image);
pictureBox1.Image = (Bitmap)image.Clone();
var oldImage = pictureBox1.Image;
var p = new Point(image.Width / 2, image.Height);
pictureBox1.Image = null;
pictureBox1.Image = RotateImage(image, p, 1);
pictureBox1.SizeMode = PictureBoxSizeMode.CenterImage;
pictureBox1.Refresh();
if (oldImage != null)
{
oldImage.Dispose();
}
}
private void button2_Click(object sender, EventArgs e)
{
Image image = new Bitmap(pictureBox1.Image);
pictureBox1.Image = (Bitmap)image.Clone();
var oldImage = pictureBox1.Image;
var p = new Point(image.Width / 2, image.Height);
pictureBox1.Image = null;
pictureBox1.Image = RotateImage(image, p, -1);
pictureBox1.SizeMode = PictureBoxSizeMode.CenterImage;
pictureBox1.Refresh();
if (oldImage != null)
{
oldImage.Dispose();
}
}
Now the problem is that when I rotate the image it gets cut. Here is the situation.
I have stretched the picture box and changed the colour of form just for clear picture.
My question is when I have used the statement
pictureBox1.Image = RotateImage(image, p, 1);
Then why is the picture not getting right after postion as this is the same statement used for any situation where we have to assign some image to groupbox. Why is not it working here? I have searched it before but the most of the searches seem irrelevant to me because they use filip function which rotate through 90,180,270. But I want to rotate by some degree maximum upto 10 degree.

Rotating Controls is not something supported by default (links talking about this: link1, link2). The reason why the picture gets cut is because, after the rotation, its width is bigger than the pictureBox1 one; thus a quick solution would be updating its size after the rotation:
pictureBox1.SizeMode = PictureBoxSizeMode.AutoSize; //Adapts the size automatically
or
pictureBox1.Width = image.Width;
pictureBox1.Height = image.Height;
This should be an acceptable solution (there has to be enough free space to account for the new dimensions of the image after being rotated anyway). The other option would be affecting the PictureBox control directly (by affecting the rectangle defining its boundaries, for example) what would be much more difficult.

Well i have come to know that win Forms are not meant for any transformations and rotations.Changing the mode to AutoSize does not make a difference. The best thing for rotation and transformation is WPF.
WPF has a good transformation classes which rotate and transform objects without affecting the object. The object does not get blurred.
You can use This for rotations and transformations.

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.