Develop Reference

How can i select drawn rectangle and clear it in Panel?

if i draw some rectangles in panel , how can i select one of them and delete it. My code here i have write it inside panel_OnClick event :
g = panel1.CreateGraphics();
Pen p = new Pen(Color.Black);
p.Width = 2;
g.DrawRectangle(p, e.X, e.Y, 100, 60);
p.Dispose();
g.Dispose();

Drawing on the panel is like drawing on a piece of paper - they are etched in and are no longer a rectangle, but a collection of pixels. Even though you could draw a rectangle over the one you want to clear using the background color, you won't be "removing the rectangle", you'll just draw a rectangle over the existing one.

Rectangle will have a Region.
You will need to subscribe to one of the following: MouseClick, MouseDown, MouseUp.
// assuming you keep a reference of the rectangle
void OnMouseClick(object sender, MouseEventArgs e) {
if(myRect.Region.IsVisible(e.Location) {
// perform action on myRect ...
// have window Invalidate(myRect)
// Refresh() the invalidated area.
}
}
This snippet assumes that no Rectangles overlap. You can also create a GraphicsPath from the points of the Rectangle and then from that path, I believe you can create a Region that enables the actual lines of the rectangle to be selected.
Update per comment
Region
GraphicsPath
I checked and I didn't see the Region property for Rectangle. So, to create the Region do the following:
var gPath = new GraphicsPath();
gPath.AddRectangle(rectangle);
var region = new Region(gPath);

I need to render an image on top of a drawn Object

I need to make a program that'll enable the user to customize his own car.
My problem is I have to draw the customizables by code and I have to add a PNG image of details on top of the drawn car.
The user has to select the colors, rim designs, and decals from the right
The car will be drawn when the PIMP button is pressed.
I have to add the PNG image, the second image, on top of the drawn image(first image), to make it look like the third image.
My current code looks like:
private void button1_Click(object sender, EventArgs e)
{
Graphics g;
g = this.CreateGraphics();
if (color == 1)
{
g.FillPolygon(blue, body);
}
else if (color ==2)
{
g.FIllPolygon(red, body);
}
g.FillPolygon(blackBrush, window);
pCard.Visible = True;
//pCard is an existing PictureBox where the Image is the cardetails.PNG
backcolor = transparent
}
When I press the PIMP button it draws the first image, but when it draws the PictureBox of cardetails.png, the transparent color displays the color gray and covers the first image.
I am very new to C# and Visual Basic. The only thing i know how to do here is to draw that blue car.

Load the image that contains the details you want to add:
Image decalImage = Image.FromFile("cardetails.png");
It would probably be best if you do not load it in your button1_Click method.
Then draw the image upon your graphics object using
g.DrawImage(decalImage, x, y);
Where x and y would be the position to draw it to.

Invalidating a graphic

I have a got a graphic object of a rectangle this is created when the button on the picturebox is clicked but if the form is moved off the screen the graphic dissapears as well as the whole form it just goes white i have tried to invalidate the picturebox but this stops the button from working can anyone help me keep the object on the form using the invalidate method i know theres a way but i can't seem to grasp it
private void squareButton_Click(object sender, EventArgs e)
{
// Declaring a new graphics object has been assigned null
Graphics objGraphics = null;
// This will create the picture graphics to be drawn in the picturebox
objGraphics = PictureBox1.CreateGraphics();
// This will redraw the picture box with a fill chosen after the systemcolors
objGraphics.Clear(SystemColors.ControlDark);
// This will draw the rectangle with a red pen 10,10 represent position and 50,50 reprsent the width and height
objGraphics.DrawRectangle(Pens.Red, 10, 10, 50, 50);
// This will draw the rectangle
objGraphics.Dispose();
invalidate(PictureBox1);
// This is not redrawing the graphic it just shows a blank form
}

Try this:
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
Graphics objGraphics = null;
// This will create the picture graphics to be drawn in the picturebox
objGraphics = e.Graphics;
// This will redraw the picture box with a fill chosen after the systemcolors
objGraphics.Clear(SystemColors.ControlDark);
// This will draw the rectangle with a red pen 10,10 represent position and 50,50 reprsent the width and height
objGraphics.DrawRectangle(Pens.Red, 10, 10, 50, 50);
// This will draw the rectangle
//objGrphics.Dispose();
}

PictureBox performing unwanted scaling C#

I currently have a windows form app with a pictureBox in the middle of it which i am drawing various images too. The images are drawing fine except for the fact that they are all being scaled up by exactly 25%. I should also add that i am drawing everything inside a Paint method, using the PaintEventArgs to get the graphics device.
Ive made sure the SizeMode is set to Normal, ive checked over and over that the scale factor of the graphics object is 1 and all the image objects that i pass to the paint method are of the size they should be, but when they get drawn they are a different size.
I have until now just been calling g.drawImage(image, Rectangle) and passing the width and height of the image as the width and height of the Rectangle so that they are forced to be drawn at the correct size but i feel that this should be a short term fix and i am overlooking something simple.
Any help would be great, thanks in advance.
Code is as follows (only the important bits):
public class Level : PictureBox
{
...
private Image image;
...
public Level(TabPage parent, Panel propertiesPanel, ItemManager items, string levelName)
{
...
image = Image.FromFile(#"Levels/" + levelName);
Size = image.Size;
SizeMode = PictureBoxSizeMode.Normal;
MouseClick += new MouseEventHandler(level_MouseClick);
MouseMove += new MouseEventHandler(level_MouseMove);
Paint += new PaintEventHandler(level_Paint);
Invalidate();
}
private void level_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
//With the rectangle fix (drawing to correct size)
g.DrawImage(image, new Rectangle(0, 0, image.Size.Width, image.Size.Height));
////Without the fix (as i thought it should be be this is where it scales it)
//g.DrawImage(image, new Point(0, 0));
drawPlacedItems(g);
drawItemPreview(g);
}

This sounds like the HorizontalResolution and VerticalResolution properties of your image are being applied when you don't want them to, modify your code as per Jeremy's link to Image sizing issue in bitmap that ensures that HorizontalResolution and VerticalResolution are reset or ignored before calling DrawImage.

how to clear panel in a simple paint application

I am working on a simple windows forms paint application. I am having problem in clearing the panel. The code i am using to draw is
private void panel1_Paint(object sender, PaintEventArgs e)
{
Graphics g = Graphics.FromImage(tempDraw);
Pen myPen = new Pen(foreColor, lineWidth);
g.DrawLine(myPen, x1, y1, x2, y2);
myPen.Width = 100;
myPen.Dispose();
e.Graphics.DrawImageUnscaled(tempDraw, 0, 0);
g.Dispose();
}
How to clear the panel?

Are drawing in the paint handler of the Panel instance? If not then calling Invalidate on the panel would do.
But you will probably be persisting the drawing items and so to clear them you would need to delete what has been drawn and then call Invalidate. You could also fill the Panel with a particular color using FillRect but that would be a dirty workaround and not fit your final design.
You should also check out CodeProject.com for examples like this one to give you an idea on what needs to be handled when creating a drawing app like this.
EDIT:
Per the edited answer, you cannot clear the panel with the existing logic. You are painting inside Paint handler of the form which will happen any time it needs to be redrawn. This means that you should change your approach. You need some sort of condition inside the Paint handler which decides whether or not it will paint anything at all. This is where the persistence of drawing objects comes in. If you want to create a drawing program then you will have to handle the mouse Down, Up and Move events over the panel objects and store the data in a points array. (As an example of one type of drawing.) Then in your Paint handler if the Points[] is not empty you draw the points. Otherwise you draw nothing... which ends up in an empty container. Then if you need to clear the drawing you delete the contents of the Points array and call Invalidate on the Panel. That will clear the persisted data and repaint to nothing.

You can use
Panel1.Invalidate();
But there is a problem with this, after you call this function it clears all the graphics from the panel, but it also recalls the function i.e.
private void panel1_Paint(object sender, PaintEventArgs e)
{
//This function is recalled after Panel1.Invalidate();
}
So solution is to make your paint code in some other function
private void MyDrawing()
{
Graphics g = Graphics.FromImage(tempDraw);
// if above line doesn't work you can use the following commented line
//Graphics g = Graphics.Panel1.CreateGraphics();
Pen myPen = new Pen(foreColor, lineWidth);
g.DrawLine(myPen, x1, y1, x2, y2);
myPen.Width = 100;
myPen.Dispose();
Panel1.Graphics.DrawImageUnscaled(tempDraw, 0, 0);
g.Dispose();
}

You'll have to draw over the panel again with whatever base colour you're using eg. white\grey with the Graphics.FillRectangle method:
// Create solid brush.
SolidBrush whiteBrush = new SolidBrush(Color.White);
// Create location and size of rectangle.
// Fill rectangle to screen.
e.Graphics.FillRectangle(whiteBrush, panel.Location.X, panel.Location.Y, panel.Width, panel.Height);
this.Invalidate();