Usually, you need to know mouse coordinates only when you handle mouse events, but then these coordinates are given to you through the event arguments parameter of your handler. Please see:
http://msdn.microsoft.com/en-us/library/system.windows.forms.mouseeventhandler%28v=vs.110%29.aspx[
^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.mouseeventargs%28v=vs.110%29.aspx[
^].
System.Windows.Forms.MouseEventArgs.X and
Y represent the coordinates in the control's coordinate system.
By the way, you can always do coordinate transform from screen coordinates to the coordinate system of your control and back:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.pointtoclient(v=vs.110).aspx[
^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.pointtoscreen(v=vs.110).aspx[
^].
This static method gives you mouse position is screen coordinates at any time, regardless of your event handling:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.mouseposition(v=vs.110).aspx[
^].
That's all on the topic of mouse coordinates.
But your major problem is different. You should not use
PictureBox; it won't help you. Even though you could solve the problem with
PictureBox, it makes no practical sense at all, would only waste your development effort and some extra resources. I'll explain what to do instead. Please see my past answers:
Append a picture within picturebox[
^],
draw a rectangle in C#[
^],
How do I clear a panel from old drawing[
^].
And these are my past answers explaining graphics rendering:
What kind of playful method is Paint? (DataGridViewImageCell.Paint(...))[
^],
capture the drawing on a panel[
^],
Drawing Lines between mdi child forms[
^],
and this one is related specifically to zoom:
Zoom image in C# .net mouse wheel[
^].
Note that zooming means
re-samling of your image, if you use a pixel graphics. Alternatively, you can do it using one of the methods
System.Drawing.Graphics.DrawImage which accept the parameter specifying the target rectangle, so it will re-sample the image when the new image size is different (take care to preserve the aspect ratio):
http://msdn.microsoft.com/en-us/library/system.drawing.graphics.drawimage%28v=vs.110%29.aspx[
^].
Before all such operations, don't forget to set appropriate re-sampling quality using this property:
http://msdn.microsoft.com/en-us/library/system.drawing.graphics.interpolationmode%28v=vs.110%29.aspx[
^].
You get the best re-sampling (interpolation) quality when you use
System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic. Please see:
http://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.interpolationmode%28v=vs.110%29.aspx[
^].
Now, this is a big warning for you: you can easily re-sample the image down, but if you want do increase the size, you can do it only slightly, otherwise your final image quality would be unacceptable.
—SA
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