We Keep Coding

Graphics getting drawn incorrectly in c# windows form

How do I make sure my graphics are drawn in the right position? I have a windows form project where the user draws lines on an Image in a pictureBox (on top of a panel). When the picture box is in default zoom the lines are drawn correctly, and they respond correctly to the Image being ragged around. However when I try to draw on the image while zoomed in/out the position of line is offset (up and to left when zoomed out, down and right when zoomed in). The pictureBox and panel are anchored on all four sides and not docked. I tried using the TranslateTransform( dx, dy ) method but it didn't work. I also tried getting rid of my CenterBox() method. How do i proceed?
Here is code for zooming:
private void trackBar1_Scroll(object sender, EventArgs e) // zoom scale
{
zoom = (float)(0.25 + 0.25 * (trackBar1.Value - 1));
if (trackBar1.Value > 0)
{
pictureBox1.Image = PictureBoxZoom(imgOriginal, new Size(trackBar1.Value, trackBar1.Value));
}
}
public Image PictureBoxZoom(Image img, Size size) //creates zoomed in clone of user image
{
sizeNewx = (Int32) (img.Width * zoom);
sizeNewy = (Int32) (img.Height * zoom);
Bitmap bm = new Bitmap(img, sizeNewx,sizeNewy);
Graphics grap = Graphics.FromImage(bm);
grap.InterpolationMode = InterpolationMode.HighQualityBicubic;
CenterBox(pictureBox1, bm);
return bm;
}
private void CenterBox(PictureBox picBox, Bitmap pic)
{
picBox.Image = pic;
picBox.Location = new Point((picBox.Parent.ClientSize.Width / 2) - (pic.Width / 2),
(picBox.Parent.ClientSize.Height / 2) - (pic.Height / 2));
picBox.Refresh();
}
Here is how graphics are drawn and zoomed:
private Stack<Line> lines = new Stack<Line>();
private void pictureBox1_MouseDown(object sender, MouseEventArgs e) //click in box
{
var mouseEventArgs2 = e as MouseEventArgs;
if (e.Button == MouseButtons.Left)
{
lines.Push(new Line { Start = mouseEventArgs2.Location });
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (lines.Count > 0 && e.Button == System.Windows.Forms.MouseButtons.Left)
{
lines.Peek().End = e.Location;
pictureBox1.Invalidate();
}
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
e.Graphics.ScaleTransform(zoom, zoom);
foreach (var line in lines)
{
Pen magenta = new Pen(Color.Magenta, 2);
e.Graphics.DrawLine(magenta, line.Start, line.End);
}
}

Ok found the issue. The problem is that the points you get in mouse move and mouse end are basically scaled, cause image is scaled and then in paint you scale them again. So you need to un scale them before paint:
private void pictureBox1_MouseDown(object sender, MouseEventArgs e) //click in box
{
var mouseEventArgs2 = e as MouseEventArgs;
if (e.Button == MouseButtons.Left)
{
Point[] pnts = new Point[ 1 ];
Matrix scaleMatrix = new Matrix( 1 / zoom, 0, 0, 1 / zoom, 0, 0 ); //un scale
pnts[0]= mouseEventArgs2.Location;
scaleMatrix.TransformPoints( pnts );
lines.Push(new Line { Start = pnts[0] });
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (lines.Count > 0 && e.Button == System.Windows.Forms.MouseButtons.Left)
{
Point[] pnts = new Point[ 1 ];
Matrix scaleMatrix = new Matrix( 1 / zoom, 0, 0, 1 / zoom, 0, 0 ); //un scale
pnts[0]= e.Location;
scaleMatrix.TransformPoints( pnts );
lines.Peek().End = pnts[0];
pictureBox1.Invalidate();
}
}

How do I reduce the flickering when the form is refreshing?

So when ever I hold the left mouse button and draw the rectangle on the form.
The form itself keeps flickering.
I've tried setting the DoubleBuffered property to true, that didnt change anything.
Is there a way to change the refresh rate or something similar?
Because from what I've tried, the example above and
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
It doesnt seem to change anything
Here is a gif showing the flickering
https://i.imgur.com/Wa3kmbM.gifv
private void Form1_Load(object sender, EventArgs e)
{
//Hide the Form
this.Hide();
label1.Visible = false;
label2.Visible = false;
//Create the Bitmap (This is an a black bitmap holding just the size.) (Bitmap is mutable)
Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
Screen.PrimaryScreen.Bounds.Height);
//Create a graphics object that's ready for alteration. `printscreen` is now a graphics Object
Graphics graphics = Graphics.FromImage(printscreen);
//Alter the graphics object which again is the printscreen
graphics.CopyFromScreen(0, 0, 0, 0, printscreen.Size);
//Create a temporary memory stream for the image
using (MemoryStream s = new MemoryStream())
{
//save graphic variable into memory
printscreen.Save(s, ImageFormat.Bmp);
//Set the size of the picturebox
pictureBox1.Size = new Size(Width, Height);
//set the value of the picturebox.Image to an Image.FromStream and load the temp stream
pictureBox1.Image = Image.FromStream(s);
}
//Show Form
this.Show();
//Cross Cursor
Cursor = Cursors.Cross;
}
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
//startX is holds the corresponding value of where the mouse is in relation to the pixels of the width
//for instance, if it's all the way to the right, it holds the value of 1920.
startX = e.X;
startY = e.Y;
selectPen = new Pen(Color.DimGray, 2);
selectPen.DashStyle = DashStyle.Dash;
pictureBox1.Refresh();
start = true;
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (start)
{
pictureBox1.Refresh();
//selectingWidth is equal to how much we have selected from the starting point.
//Let's say the starting point is 10 and our current mouse position is at 10 then we have selected 0 pixels to the right.
//However if we move our mouse 10 pixels to the right it means we have selected 10 pixels to the right.
selectingWidth = e.X - startX;
selectingHeight = e.Y - startY;
//if the selectingWidth is less than 0, then set the origin to the current position of the mouse.
var drawfromX = selectingWidth < 0 ? e.X : startX;
var drawfromY = selectingHeight < 0 ? e.Y : startY;
pictureBox1.Refresh();
pictureBox1.CreateGraphics().DrawRectangle(selectPen,
drawfromX,
drawfromY,
Math.Abs(selectingWidth),
Math.Abs(selectingHeight));
}
}

Why can't it draw a rectangle the opposite way?

So I am trying to recreate the Snipping Tool that comes with Windows.
However I've manage to get it to draw a rectangle from the top left corner and then when I move my cursor to the bottom right.
However if I try to move my cursor from let's say the middle of the screen to the top left it doesnt draw the rectangle.
Why is this?
Here is a GIF showing what happends
https://i.imgur.com/0Y7xXnS.gifv
//These variables control the mouse position
int selectX;
int selectY;
int selectWidth;
int selectHeight;
public Pen selectPen;
//This variable control when you start the right click
bool start;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
//Hide the Form
this.Hide();
//Create the Bitmap (This is an a black bitmap holding just the size.) (Bitmap is mutable)
Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
Screen.PrimaryScreen.Bounds.Height);
//Create a graphics object that's ready for alteration. `printscreen` is now a graphics Object
Graphics graphics = Graphics.FromImage(printscreen);
//Alter the graphics object which again is the printscreen
graphics.CopyFromScreen(0, 0, 0, 0, printscreen.Size);
//Create a temporary memory stream for the image
using (MemoryStream s = new MemoryStream())
{
//save graphic variable into memory
printscreen.Save(s, ImageFormat.Bmp);
//Set the size of the picturebox
pictureBox1.Size = new Size(Width, Height);
//set the value of the picturebox.Image to an Image.FromStream and load the temp stream
pictureBox1.Image = Image.FromStream(s);
}
//Show Form
this.Show();
//Cross Cursor
Cursor = Cursors.Cross;
}
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
selectX = e.X;
selectY = e.Y;
selectPen = new Pen(Color.DimGray, 1);
selectPen.DashStyle = DashStyle.Solid;
pictureBox1.Refresh();
start = true;
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (start)
{
selectWidth = e.X - selectX;
selectHeight = e.Y - selectY;
pictureBox1.Refresh();
pictureBox1.CreateGraphics().DrawRectangle(selectPen,
selectX, selectY, selectWidth, selectHeight);
}
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
Stream sound = Resources.SnapshotSound;
SoundPlayer player = new SoundPlayer(sound);
player.PlaySync();
Application.Exit();
}
}

So what you end up with is basically a rectangle with a negative width and height.
You'll probably want to use the Math.Abs to make sure you get a proper width and height in the cases the difference would become negative.
With that, you will also probably want to draw from different positions based on where your cursor is in relation to the selected point. Something like
selectWidth = e.X - selectX;
selectHeight = e.Y - selectY;
// If width is less than 0, draw from pointer, otherwise from select X
var drawFromX = selectWidth < 0 ? e.X : selectX;
// If height is less than 0, draw from pointer, otherwise from select Y
var drawFromY = selectHeight < 0 ? e.Y : selectY;
pictureBox1.Refresh();
pictureBox1.CreateGraphics().DrawRectangle(selectPen,
drawFromX,
drawFromY,
Math.Abs(selectWidth), // Make sure the rectangle width is positive
Math.Abs(selectHeight)); // Make sure the rectangle height is positive

Draw on pictureBox with mouse

I am trying to make a paint program in C# I started out using a panel, and using a pen, but whenever the window refreshed, the drawing was removed.
What program is meant to do:
Open image, allow user to draw on it, and allow user to save modified image
Old code:
private void canvas_MouseMove(object sender, MouseEventArgs e)
{
if (canDraw)
{
//canvas.BackgroundImage = buffer;
if (drawSquare)
{
isDrawn = true;
SolidBrush sb = new SolidBrush(btn_brushColor.BackColor);
Rectangle path1 = new Rectangle(e.X, e.Y, int.Parse(shapeSize.Text), int.Parse(shapeSize.Text));
//Rectangle path1 = new Rectangle(100, 100, int.Parse(shapeSize.Text), int.Parse(shapeSize.Text));
Rectangle path2 = new Rectangle(e.X + (int.Parse(shapeSize.Text) / 20), e.Y + (int.Parse(shapeSize.Text) / 20), (int.Parse(shapeSize.Text) / 10 * 9), (int.Parse(shapeSize.Text) / 10 * 9));
//Rectangle path2 = new Rectangle(e.X, e.Y, 2/(int.Parse(shapeSize.Text)), 2/(int.Parse(shapeSize.Text)));
// Create a region from the Outer circle.
Region region = new Region(path1);
// Exclude the Inner circle from the region
region.Exclude(path2);
// Draw the region to your Graphics object
g.FillRegion(sb, region);
//drawRectangle = false;
debug.Text = ("recf");
}
if (drawEraser)
{
isDrawn = true;
Pen d = new Pen(Color.White, float.Parse(cmb_brushSize.Text));
g.DrawLine(d, new Point(initX ?? e.X, initY ?? e.Y), new Point(e.X, e.Y));
initX = e.X;
initY = e.Y;
}
if (drawbrush)
{
isDrawn = true;
Pen p = new Pen(btn_brushColor.BackColor, float.Parse(cmb_brushSize.Text));
g.DrawLine(p, new Point(initX ?? e.X, initY ?? e.Y), new Point(e.X, e.Y));
initX = e.X;
initY = e.Y;
}
}
}
private void canvas_MouseDown(object sender, MouseEventArgs e)
{
debug.Text = ("running");
canDraw = true;
}
private void canvas_MouseUp(object sender, MouseEventArgs e)
{
canDraw = false;
initX = null;
initY = null;
}
I am trying to use picBox_Paint(PaintEventArgs...) to draw, but I can't figure out how to capture _MouseDown/_MouseMove/_MouseUp with the paint event to draw when the mouse is moved over the pictureBox and MouseDown is true.
Or if there is a way to make DrawLine on mouseEvent Permanent.
Current code:
private void picBox_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
Graphics g = e.Graphics;
g.DrawString("This is a diagonal line drawn on the control",
new Font("Arial", 10), System.Drawing.Brushes.Blue, new Point(30, 30));
g.DrawLine(System.Drawing.Pens.Red, picBox.Left, picBox.Top,
picBox.Right, picBox.Bottom);
}
This works, and does't get removed on window refresh, but I don't know how to get mouse input now, and use MouseEvent to get the mouse points for drawing.

Using control functions in a bitmap in C#

I was thinking of implementing a bitmap into a picturebox (or the otherway round), such that I could have the option to:
1.drag and drop the item (Control function with mousebuttons)
2.rotate the item (bitmap function).
This is what I have currently:
Bitmap bmp = new Bitmap(#"my source");
PictureBox item = new System.Windows.Forms.PictureBox();
I create the picturebox on the click of a button:
private void button2_Click(object sender, EventArgs e)
{
item.BackColor = Color.Blue;
item.Location = new Point(400, 200);
item.MouseDown += new MouseEventHandler(textbox_MouseDown);
item.MouseMove += new MouseEventHandler(textbox_MouseMove);
item.MouseUp += new MouseEventHandler(textbox_MouseUp);
item.MouseWheel += new MouseEventHandler(textbox_MouseWheel);
item.Image = bmp;
item.SizeMode = PictureBoxSizeMode.StretchImage;
this.Controls.Add(item);
item.BringToFront();
}
and in the textbox_MouseMove void, I try to use the middle button to signal the rotation of the image
void textbox_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Middle )
{
if (activeControl == null || activeControl != sender)
{
return;
}
this.Paint += new PaintEventHandler(objectrotation_Paint);
Invalidate();
}
}
where the PaintEvent is responsible for the rotation of the image
private void objectrotation_Paint(object sender, PaintEventArgs d)
{
int dpi = 96;
bmp.SetResolution(dpi, dpi);
if (bmp != null)
{
float bw2 = bmp.Width / 2f;
float bh2 = bmp.Height / 2f;
d.Graphics.TranslateTransform(bw2, bh2);
d.Graphics.RotateTransform(angle);
d.Graphics.TranslateTransform(-bw2, -bh2);
d.Graphics.DrawImage(bmp,0,0);
d.Graphics.ResetTransform();
}
}
This however would create two sets of images, i.e. when I press button 2 I get one image, when I move my mouse with middle button down I get the second image (rotating).Refering to some of the questions on here, people recommend using
item.Image = bmp;
but it simply copies the from picturebox to the bitmap while they have seperate controls. While the picturebox class could not perform rotations without implementing a Bitmap, the Bitmap class does not have the option to perform actions like OnMouseMove etc.
Is there any way to combine my bitmap and the picturebox such that I could achieve my two goals?