Andy De George
c0ba284473
* Merge winforms framework content to working branch (#14) * Breadcrumb / TOC / Move net5 to net folder (#15) * change path from net5 to net * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Mess with bread/toc * Add .net 5 winforms placeholder article (#16) * added some metadata and adjusted net5 placeholder * corrections * corrections * corrections * Test1 * Swapping landing page vs concept * fix links * Fix links * Fix desc
2.7 KiB
title, ms.date, dev_langs, helpviewer_keywords, ms.assetid
| title | ms.date | dev_langs | helpviewer_keywords | ms.assetid | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| How to: Draw Opaque and Semitransparent Lines | 03/30/2017 |
|
|
8f2508af-f495-4223-b5cc-646cbbb520eb |
How to: Draw Opaque and Semitransparent Lines
When you draw a line, you must pass a xref:System.Drawing.Pen object to the xref:System.Drawing.Graphics.DrawLine%2A method of the xref:System.Drawing.Graphics class. One of the parameters of the xref:System.Drawing.Pen.%23ctor%2A constructor is a xref:System.Drawing.Color object. To draw an opaque line, set the alpha component of the color to 255. To draw a semitransparent line, set the alpha component to any value from 1 through 254.
When you draw a semitransparent line over a background, the color of the line is blended with the colors of the background. The alpha component specifies how the line and background colors are mixed; alpha values near 0 place more weight on the background colors, and alpha values near 255 place more weight on the line color.
Example
The following example draws a bitmap and then draws three lines that use the bitmap as a background. The first line uses an alpha component of 255, so it is opaque. The second and third lines use an alpha component of 128, so they are semitransparent; you can see the background image through the lines. The statement that sets the xref:System.Drawing.Graphics.CompositingQuality%2A property causes the blending for the third line to be done in conjunction with gamma correction.
[!code-csharpSystem.Drawing.AlphaBlending#11] [!code-vbSystem.Drawing.AlphaBlending#11]
The following illustration shows the output of the following code:
Compiling the Code
The preceding example is designed for use with Windows Forms, and it requires xref:System.Windows.Forms.PaintEventArgs e, which is a parameter of the xref:System.Windows.Forms.Control.Paint event handler.