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Crop correct part of image while the PictureBox is in 'zoom' mode [duplicate]

This question already has an answer here:
Draw Rectangle inside picture box SizeMode Zoom
(1 answer)
Closed 3 years ago.
I have a PictureBox1 with it's sizemode set to Stretch and PictureBox1. The PictureBox1 contains an image and let's me select part of it and then crop it and store the cropped part inside PictureBox2. It works great when the sizemode is set to Stretch and the picture is not zoomed, but not when I zoom it or set the sizemode to zoom.
working example - sizemode set to 'stretch'
The code I use to crop part of the picture (original source)
try
{
float stretch1X = 1f * pictureBox1.Image.Width / pictureBox1.ClientSize.Width;
float stretch1Y = 1f * pictureBox1.Image.Height / pictureBox1.ClientSize.Height;
Point pt = new Point((int)(_mDown.X * stretch1X), (int)(_mDown.Y * stretch1Y));
Size sz = new Size((int)((_mCurr.X - _mDown.X) * stretch1X),
(int)((_mCurr.Y - _mDown.Y) * stretch1Y));
if (sz.Width > 0 && sz.Height > 0)
{
Rectangle rSrc = new Rectangle(pt, sz);
Rectangle rDest = new Rectangle(Point.Empty, sz);
Bitmap bmp = new Bitmap(sz.Width, sz.Height);
using (Graphics G = Graphics.FromImage(bmp))
G.DrawImage(pictureBox1.Image, rDest, rSrc, GraphicsUnit.Pixel);
return bmp;
}
return null;
}
catch (Exception ex)
{
throw ex;
}
How do I calculate it properly? How can I make the crop function work in a way so it lets the user zoom in/out and still crop the correct part of the picture?

You need to calculate the points using the stretch factor and maybe also the offset.
For Zoom there is only one factor as aspect ratio is always the same for Image and PictureBox, but there usually is an offset; for Stretch you need no offset but two factors.
Here is an example that goes all the way using two PictureBoxes two show a zoomed version and the cropped bitmap. It makes use of an all-purpose function ImageArea that determines size and offset.
Two class level variables:
Point pDown = Point.Empty;
Rectangle rect = Rectangle.Empty;
Three mouse events:
private void PictureBox1_MouseDown(object sender, MouseEventArgs e)
{
pDown = e.Location;
pictureBox1.Refresh();
}
private void PictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if (!e.Button.HasFlag(MouseButtons.Left)) return;
rect = new Rectangle(pDown, new Size(e.X - pDown.X, e.Y - pDown.Y));
using (Graphics g = pictureBox1.CreateGraphics())
{
pictureBox1.Refresh();
g.DrawRectangle(Pens.Orange, rect);
}
}
private void PictureBox1_MouseUp(object sender, MouseEventArgs e)
{
Rectangle iR = ImageArea(pictureBox2);
rect = new Rectangle(pDown.X - iR.X, pDown.Y - iR.Y,
e.X - pDown.X, e.Y - pDown.Y);
Rectangle rectSrc = Scaled(rect, pictureBox2, true);
Rectangle rectDest = new Rectangle(Point.Empty, rectSrc.Size);
Bitmap bmp = new Bitmap(rectDest.Width, rectDest.Height);
using (Graphics g = Graphics.FromImage(bmp))
{
g.DrawImage(pictureBox2.Image, rectDest, rectSrc, GraphicsUnit.Pixel);
}
pictureBox2.Image = bmp;
}
Here is a useful function that returns the area of the actual image inside a picturebox for any sizemode..:
Rectangle ImageArea(PictureBox pbox)
{
Size si = pbox.Image.Size;
Size sp = pbox.ClientSize;
if (pbox.SizeMode == PictureBoxSizeMode.StretchImage)
return pbox.ClientRectangle;
if (pbox.SizeMode == PictureBoxSizeMode.Normal ||
pbox.SizeMode == PictureBoxSizeMode.AutoSize)
return new Rectangle(Point.Empty, si);
if (pbox.SizeMode == PictureBoxSizeMode.CenterImage)
return new Rectangle(new Point((sp.Width - si.Width) / 2,
(sp.Height - si.Height) / 2), si);
// PictureBoxSizeMode.Zoom
float ri = 1f * si.Width / si.Height;
float rp = 1f * sp.Width / sp.Height;
if (rp > ri)
{
int width = si.Width * sp.Height / si.Height;
int left = (sp.Width - width) / 2;
return new Rectangle(left, 0, width, sp.Height);
}
else
{
int height = si.Height * sp.Width / si.Width;
int top = (sp.Height - height) / 2;
return new Rectangle(0, top, sp.Width, height);
}
}
We only need the offset to determine the rectangle unscaled. We also need to scale it:
Rectangle Scaled(Rectangle rect, PictureBox pbox, bool scale)
{
float factor = GetFactor(pbox);
if (!scale) factor = 1f / factor;
return Rectangle.Round(new RectangleF(rect.X * factor, rect.Y * factor,
rect.Width * factor, rect.Height * factor));
}
For this need to know the scaling factor, which depends on the aspect ratio:
float GetFactor(PictureBox pBox)
{
if (pBox.Image == null) return 0;
Size si = pBox.Image.Size;
Size sp = pBox.ClientSize;
float ri = 1f * si.Width / si.Height;
float rp = 1f * sp.Width / sp.Height;
float factor = 1f * pBox.Image.Width / pBox.ClientSize.Width;
if (rp > ri) factor = 1f * pBox.Image.Height / pBox.ClientSize.Height;
return factor;
}
This solution will also work if the PictureBox is zoomed in or out by placing it inside a AutoScrolling Panel and changing the Pbox.Size.

How can I clear the Graphics before drawing another letter?

private void timer1_Tick(object sender, EventArgs e)
{
counter--;
DrawLetter();
if (counter == 0)
{
t.Stop();
TakeScreenShot();
}
}
private void DrawLetter()
{
var letter = counter.ToString();
Graphics g = Graphics.FromHdc(GetDC(IntPtr.Zero));
float width = ((float)this.ClientRectangle.Width);
float height = ((float)this.ClientRectangle.Width);
float emSize = height;
Font font = new Font(FontFamily.GenericSansSerif, emSize, FontStyle.Regular);
font = FindBestFitFont(g, letter.ToString(), font, this.ClientRectangle.Size);
SizeF size = g.MeasureString(letter.ToString(), font);
g.DrawString(letter, font, new SolidBrush(Color.White), (width - size.Width) / 2, 0);
}
private Font FindBestFitFont(Graphics g, String text, Font font, Size proposedSize)
{
// Compute actual size, shrink if needed
while (true)
{
SizeF size = g.MeasureString(text, font);
// It fits, back out
if (size.Height <= proposedSize.Height &&
size.Width <= proposedSize.Width) { return font; }
// Try a smaller font (90% of old size)
Font oldFont = font;
font = new Font(font.Name, (float)(font.Size * .9), font.Style);
oldFont.Dispose();
}
}
void TakeScreenShot()
{
bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);
gfxScreenshot = Graphics.FromImage(bmpScreenshot);
gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
bmpScreenshot.Save(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) + #"\ScreenCaptures\newfile.png", ImageFormat.Png);
}
I am able to draw the string but it is writing on top of itself.
How can I clear it? Basically I want the countdown to appear on the screen then take a screenshot.
Right now the number is overwritten by another.

You can do the following: create an additional transparent form, and it will display timer values. This will allow you to erase the previous value. In addition, this will allow to get rid of the function call GetDC via PInvoke.
Form timerForm; // main form field
// Create and show additional transparent form before starting the timer
timerForm = new Form
{
FormBorderStyle = FormBorderStyle.None,
WindowState = FormWindowState.Maximized,
TransparencyKey = SystemColors.Control,
ShowInTaskbar = false
};
timerForm.Show();
timer.Start();
Change the method DrawLetter as follows
private void DrawLetter()
{
var letter = counter.ToString();
Graphics g = timerForm.CreateGraphics();
float width = ClientRectangle.Width;
float height = ClientRectangle.Width;
float emSize = height;
using (Font font1 = new Font(FontFamily.GenericSansSerif, emSize, FontStyle.Regular))
using (Font font2 = FindBestFitFont(g, letter, font1, ClientRectangle.Size))
using (var brush = new SolidBrush(Color.White))
{
SizeF size = g.MeasureString(letter, font2);
g.Clear(SystemColors.Control);
g.DrawString(letter, font2, brush, (width - size.Width) / 2, 0);
}
}
We must release all used resources like fonts and brushes. For this I applied using.
Change the timer tick event handler as follows
private void timer1_Tick(object sender, EventArgs e)
{
counter--;
DrawLetter();
if (counter == 0)
{
timer.Stop();
TakeScreenShot();
timerForm.Dispose(); // must release
}
}
FindBestFitFont and TakeScreenShot methods remain unchanged.

Draw your font to a different bitmap. Transparent background (or whatever doesn't invert, see below - perhaps black).
(now you could also draw it with a different colored shadow to mitigate drawing on similar colored background - but the natures of SRCINVERT/XOR, below, will mitigate this as well)
Use BitBlt to copy it to the screen
Use the SRCINVERT raster op.
(note: the colors may be different as it is XORing it with pixels underneath)
Now when is is time to erase, just make the same bitblt with the same contents as previous, the double XOR effect caused by SRCINVERT will have the effect of erasing it.
Then draw the next font.
Note: if desktop is updated between calls, all bets are off.
better...
Rather than attempting a transparent background, draw it on a white background. This will eliminate contrast issues with the font, eliminate concern with dynamic updates, and eliminate problems with erasing. Sometimes you have to admit - the method & code isn't the problem, the requirements are the problem. This all depends of course on the source of the requirements, etc.
If it needs to look professional, don't put the content on the screen, draw it after you take the screen capture.
If you end up using the transparent window approach, the screen shot may miss the transparent window. To get it, see this question:
Capture screenshot Including Semitransparent windows in .NET. (could be fixed by newer .net / newer windows versions)

You need to invalidate all the windows on the desktop by using the InvalidateRect function to erase the previously drawn letter.
See additional codes below for the DrawLetter method.
[DllImport("user32")]
private static extern bool InvalidateRect(IntPtr hwnd, IntPtr rect, bool bErase);
private void DrawLetter()
{
var letter = counter.ToString();
Graphics g = Graphics.FromHdc(GetDC(IntPtr.Zero));
float width = ((float)this.ClientRectangle.Width);
float height = ((float)this.ClientRectangle.Width);
float emSize = height;
Font font = new Font(FontFamily.GenericSansSerif, emSize, FontStyle.Regular);
font = FindBestFitFont(g, letter.ToString(), font, this.ClientRectangle.Size);
SizeF size = g.MeasureString(letter.ToString(), font);
// Invalidate all the windows.
InvalidateRect(IntPtr.Zero, IntPtr.Zero, true);
// Sometimes, the letter is drawn before the windows are invalidated.
// To fix that, add a small delay before drawing the letter.
System.Threading.Thread.Sleep(100);
// Finally, draw the letter.
g.DrawString(letter, font, new SolidBrush(Color.White), (width - size.Width) / 2, 0);
}

A solution is:
You must take a snapshot of that area you want to show counter before all things. Then call DrawImage function to draw snapshot image before call DrawString function every time.

Image-map click events in zoomable image

I've got a large zoomable* image (loaded once using canvas nested in a ViewportControl) and I want to implement the following functionality:
The image should have several clickable areas attached that move along the image when the user zooms in/out, pinch, moves around etc.
Think about an image of a map from which I should get click events from specific areas.
I haven't figured out whether these areas should be re-attached when the user zooms or if I could attach them once.
Any ideas?
*I used the pinch and zoom code from this sample: http://code.msdn.microsoft.com/wpapps/Image-Recipes-0c0b8fee
edit:
I'm trying to make a single temp button work using the DeltaScale property of the zoom functionality.
These are two main function:
void OnManipulationDelta(object sender, ManipulationDeltaEventArgs e)
{
if (e.PinchManipulation != null)
{
e.Handled = true;
if (!_pinching)
{
_pinching = true;
Point center = e.PinchManipulation.Original.Center;
_relativeMidpoint = new Point(center.X / TestImage.ActualWidth, center.Y / TestImage.ActualHeight);
var xform = TestImage.TransformToVisual(viewport);
_screenMidpoint = xform.Transform(center);
}
_scale = _originalScale * e.PinchManipulation.CumulativeScale;
// sample double variables for storing the changes of scaling
// initial values of mytop & myleft are the initial actual spot of tempbtn on the image
mytop = e.PinchManipulation.DeltaScale * mytop;
myleft = e.PinchManipulation.DeltaScale * myleft;
CoerceScale(false);
ResizeImage(false);
}
else if (_pinching)
{
_pinching = false;
_originalScale = _scale = _coercedScale;
}
}
void OnManipulationCompleted(object sender, ManipulationCompletedEventArgs e)
{
_pinching = false;
_scale = _coercedScale;
Canvas.SetTop(tempbtn, mytop);
Canvas.SetLeft(tempbtn, myleft);
}
The resizing function for the main image in the background:
void ResizeImage(bool center)
{
if (_coercedScale != 0 && _bitmap != null)
{
double newWidth = canvas.Width = Math.Round(_bitmap.PixelWidth * _coercedScale);
double newHeight = canvas.Height = Math.Round(_bitmap.PixelHeight * _coercedScale);
xform.ScaleX = xform.ScaleY = _coercedScale;
viewport.Bounds = new Rect(0, 0, newWidth, newHeight);
if (center)
{
viewport.SetViewportOrigin(
new Point(
Math.Round((newWidth - viewport.ActualWidth) / 2),
Math.Round((newHeight - viewport.ActualHeight) / 2)
));
}
else
{
Point newImgMid = new Point(newWidth * _relativeMidpoint.X, newHeight * _relativeMidpoint.Y);
Point origin = new Point(newImgMid.X - _screenMidpoint.X, newImgMid.Y - _screenMidpoint.Y);
viewport.SetViewportOrigin(origin);
}
}
}
The problem is that my button always stands a little bit (around 10px, gets more as I zoom) to the top & left of the actual place I want it positioned. Something causes this deviation but I can't find out where's the problem. Any guesses/suggestions?

How to draw the sharpest possible image?

I know most people are always trying to get smooth settings but this time, since I am printing a barcode, I need to find out how to tell e.Graphics to print my image with the sharpest possible settings. Keep in mind that my current settings produce the best I was able to test so far but, once i print it to a file and zoom in 500%, you can still see a bit of smoothness.
Here's my code so far:
private void printDocument1_PrintPage_1(object sender, PrintPageEventArgs e)
{
double pdf417_widthDPI = Math.Round(((double)picpdf417.Image.Width / (double)288) * 2, 2);
double pdf417_heightDPI = Math.Round(((double)picpdf417.Image.Height / (double)288) * 2, 2);
int newWidth = (int)Math.Round(pdf417_widthDPI * 96);
int newHeight = (int)Math.Round(pdf417_heightDPI * 96);
Rectangle pdf417_location_size = new Rectangle(0, 100, newWidth, newHeight);
e.Graphics.CompositingQuality = CompositingQuality.HighSpeed;
e.Graphics.SmoothingMode = SmoothingMode.None;
e.Graphics.InterpolationMode = InterpolationMode.Low;
e.Graphics.PixelOffsetMode = PixelOffsetMode.None;
e.Graphics.DrawImage(picpdf417.Image, pdf417_location_size);
}

Is it possible to rotate a button control in WinForms?

Is it possible to rotate a button or any control at a particular angle in WinForms? If so, how?

If you really want to (I have no idea why one would..*) you could try to use a Button subclass, maybe like that:
public partial class TurnButton : Button
{
public TurnButton()
{
InitializeComponent();
}
int angle = 0; // current rotation
Point oMid; // original center
protected override void OnLayout(LayoutEventArgs levent)
{
base.OnLayout(levent);
if (oMid == Point.Empty) oMid = new Point(Left + Width / 2, Top + Height / 2);
}
protected override void OnPaint(PaintEventArgs pe)
{
int mx = this.Size.Width / 2;
int my = this.Size.Height / 2;
SizeF size = pe.Graphics.MeasureString(Text, Font);
string t_ = Text;
Text = "";
base.OnPaint(pe);
if (!this.DesignMode)
{
Text = t_; pe.Graphics.TranslateTransform(mx, my);
pe.Graphics.RotateTransform(angle);
pe.Graphics.TranslateTransform(-mx, -my);
pe.Graphics.DrawString(Text, Font, SystemBrushes.ControlText,
mx - (int)size.Width / 2, my - (int)size.Height / 2);
}
}
protected override void OnClick(EventArgs e)
{
this.Size = new Size(Height, Width);
this.Location = new Point(oMid.X - Width / 2, oMid.Y - Height / 2);
angle = (angle + 90) % 360;
Text = angle + "°";
base.OnClick(e);
}
}
(* I have no idea why I wrote that, either ;-)

You can't rotate controls. That's simply not supported by the native API controls that WinForms uses.
And one might wonder why it even should be supported. What could you possibly be trying to do that you'd need to rotate a button control? It would be much easier to draw it in a different place with a different shape in the first place, rather than trying to rotate an existing control. (Do note that you can also resize and reposition a control at run-time, if that would fit your needs. Investigate the Size and Location properties.)
The only workaround is to draw the control's image to a bitmap, hide the control, and draw the bitmap onto the form in the location you want it to appear. Of course, that won't result in a control that the user can interact with. They won't be able to click an image of a button, because it's not a real button. If that's acceptable to you, you should probably be using an image in the first place, rather than a button.

This is similar to the question asked here:
Rotating a .NET panel in Windows Forms
The quick summary of answers from that question is that while it may be possible to do it, it would be very, very complicated.

A possible workaround in some cases would be this:
Use a tabControl , and resize it so you only have the button left. Set the allignment to left/right, and you have your button rotated 90/270 degrees.

public class VerticalButton : Button
{
public string VirticalText { get; set; }
protected override void OnPaint(PaintEventArgs pe)
{
base.OnPaint(pe);
StringFormat stringFormat = new StringFormat();
stringFormat.FormatFlags = StringFormatFlags.DirectionVertical;
SolidBrush solidBrush = new SolidBrush(this.ForeColor);
stringFormat.Alignment = StringAlignment.Center;
stringFormat.LineAlignment = StringAlignment.Center;
pe.Graphics.DrawString(VirticalText, this.Font, solidBrush,
new Rectangle(0, 0, Width, Height), stringFormat);
}
}