The color pickers window


Some years ago I started to write my first color picker application in VB 6.0. For me it was useful, because it helped me to pick colors for my website projects very fast. Since then I released two other releases as the freeware "ColorManager" (did you hear about it?).

The only thing I didn't like: I used API functions directly via DllImport in the last .NET 1.x release version. I used them because I started the first ColorManager in VB 6.0 and I had to. Now I'm developing in C# and I want to use the power of .NET, not Win32 directly. So I decided to write a new ColorManager kernel version with pure C# code - here it is.
By the way, I decided to implement an option to use W32 API methods to make screenshots because the standard C# method doesn't copy alpha / layered screen areas. The use of these methods is optional and disabled by default.

I've written a user control that works like a magnifying glass: Move the mouse 'round your screen and you'll see the part of the screen that the cursor is pointing to, bigger. You can deactivate the pixel and position view in the display, if you don't need it. Click on the display to create a magnifying glass with alpha effect that will follow the cursor. Move the mouse wheel while the moving glass is active to increase or decrease it's magnifying values.

The sample application is a test project for the new ColorManager. The current pixel under the cursor will be selected if the window looses the focus (just click on the pixel to select the color) or you click while the moving glass is active. The window will try to get the focus again after selecting a pixel. Finally the RGB values and the preview of the color will stay at the window bottom and the application is ready to select the next color.
Next step would be to make the user able to copy the values to the clipboard, provide the hex value for websites, and so on... But this is for the new ColorManager - here you get a small user control for your own applications.

Using the code

You find the main class MagnifyingGlass in the file MagnifyingGlass.cs. The class inherits from a usercontrol and provides these additional properties, methods and events:


The magnification ratio. 5 to size one pixel to 5x5 pixels. (The value should be a number that can not be divided with 2, minimum is 3.)


The range of the display, beginning from the pixel to the top, the bottom, the left and the right (minimum is 1)


Show the current pixel in the display


Show the current position in the upper left corner of the display


Where to display the position coordinates (somewhere, but not in the middle)


The display format for the position corrdinates (#x and #y is used for the values)


The timer that will update the display in an interval


The color of the current pixel


This event is fired after the display has been updated by the timer or the moving glass


This event is fired before the moving glass is making a screenshot which will be used as screen image (maybe you want to hide something?)


This event is fired after the moving glass made a screenshot


The MagnifyingGlass instance for the moving glass

SetNewSize(int pixelSize, int pixelRange)

To set both values that will be used to recalculate the controls dimensions


Enable or disable the moving glass feature (always disabled, if disabled trough the constructor!)


Enable or disable the use of W32 API methods to make a screenshot (static property)

You should not resize the control: The size will be calculated using the PixelSize and PixelRange settings. The font is taken from the Font property, the font color from the ForeColor property. The color for the space out of the desktop (or the screen) and the background of the position display is taken from the BackColor property.

I used a special interpolation mode to disable the smoothing effect when painting the image scaled:

e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.NearestNeighbor;

Without this setting it's hard to find a single pixel in the magnified screenshot view.

Example code to display the control with default settings on your form (place this within the form class and call the method):

private void AddMagnifyingGlassControl()
	MagnifyingGlass mg = new MagnifyingGlass();
	// Set the position and maybe other settings to the "mg" object here

Note: To use the control within a designer, add the class to your project and compile once. You will then find the control in the Visual Studio Toolbox. Add it to your form like you do with any other control.

By the way, you can decide if you want to use the moving glass feature. Simply use the constructor with the boolean value:

// Disable the moving glass
	MagnifyingGlass mg = new MagnifyingGlass(false);

// Enable the moving glass
	MagnifyingGlass mg = new MagnifyingGlass(true);
// or:
	MagnifyingGlass mg = new MagnifyingGlass();

If you disable the moving glass trough the constructor, you won't be able to enable it later (you need to create a new MagnifyingGlass instance with moving glass). Disabling at construction time is only provided so save some memory, if you really don't want to use the moving glass feature.

You may also use only the moving glass without placing the fixed Control to your form. Example:

private void ShowMovingGlass()
	MovingMagnifyingGlass mg = new MovingMagnifyingGlass();

Any suggestions? You're welcome!

Known bugs

Points of Interest

Writing the calculation of the screenshot sizes and display positions was... yeah... (I wrote the complete code (the first version) in - lets say - round about 30 minutes) I hope everything is working right :)
Edit: I should take more time for testing ;) The first bugfix is released.

Someone told me that his graphic card CPU cooler is running faster (and louder) after he started an application with the magnifying glass control on it's form, even if the UpdateTimer was stopped. I don't think it's my mistake, but maybe someone knows if the control really takes graphic CPU power while it's not running??? Currently I think it's simply a bug in the software that is controlling the cooler fan's speed or something else need more graphic CPU power.

The default C# screen capturing method does not capture alpha / layered screen areas. For this we need to use W32 API methods (optional, disabled by default):

        private Bitmap MakeScreenshot(Rectangle rect)
            // Capture an rectangle area from the screen
            Bitmap bmp = new Bitmap(rect.Width, rect.Height);
            using (Graphics g = Graphics.FromImage(bmp))
                if (UseWin32Api)
                    // We're using BitBlt from the GDI API to copy alpha / layered screen regions also
                    IntPtr gHdc = g.GetHdc();
                    IntPtr dHdc = W32.GetDesktopWindow();
                    IntPtr wHdc = W32.GetWindowDC(dHdc);
                    W32.BitBlt(gHdc, 0, 0, bmp.Width, bmp.Height, wHdc, rect.X, rect.Y, W32.SRCCOPY | W32.CAPTUREBLT);
                    W32.ReleaseDC(dHdc, wHdc);
                    gHdc = IntPtr.Zero;
                    dHdc = IntPtr.Zero;
                    wHdc = IntPtr.Zero;
                    // The standard C# screen capturing
                    g.CopyFromScreen(rect.Location, new Point(0, 0), bmp.Size);
            return bmp;

If you'd like to get the current freeware release of the ColorManager (sorry, no source), you can download it from here: (527 KB)