PictureBoxGradient UserControl

By Chris Richner, 1 Nov 2002

Add a reason or comment to your vote: x
Votes of 3 or less require a comment

Sample Image - PictureBoxGradient.jpg

Introduction

My first article was based on a class which only draws the Gradient progress line. I guess there was too much work to use it. My idea was to drag a new control to my form, set the properties to what I like, and everything should work.

This new Control replaces the old version and is ready to use, extended by the most important properties from PictureBox and Gradient Class. It uses a Thread based Timer Class to redraw itself. With this timer it is possible to draw the Gradient while you're doing hard work behind the scenes.

How to use it

Drag PictureBoxGradient User Control from Toolbox to your form
Extend "PictureBox" Tab in "Property" Toolwindow, select a image
Extend "Gradient" Tab and choose colors to draws Gradient, e.g. Color1 white and Color2 orange
```
this.pictureBoxGradient1.Start()
```

and you're finished.

To use the gradient call Start and Stop

Key Benefits

MSDN styled Help File included, created with NDoc (great freeware).
Easy to use, no great library is used, just copy the UserControl to your code and change Namespace.
Easy customizable, every property can altered via Property ToolWindow.
Compact design, black boxed in only one control.
100% C#, no API's used.

How it works

The User Control is based on a PictureBox in which SizeMode is set to AutoSize. The height property of PictureBox is extended by the GradientHeight Property. When you choose a Image the control resize itself to reflect changes made to the Image Property.

The Gradient is basically drawn with four LinearGradientBrush and two SolidBrush classes. mainRect is the Rectangle in which we have to draw. The Gradient will move from Position 0 to mainRect.Width.

The problem is that the Gradient will move out on the right side, and at the same time it will move in at the left side. It seems like the Gradient would cycle and never leave the Rectangle. Because of this we need four LinearGradientBrush and not only two. We need also two SolidBrush to fill the region which is not affected by the Gradient. These brushes are created with the two colors used for Gradient.

These Properties are important for drawing:

GradientHeight height of Gradient.

GradientSizeInProcent Gradient size in % relative to the given width.

Rectangle Gradient rectangle ( GradientHeight included ).

Color1 and Color2 used for LinearGradientBrush.

Step Stepsize in Pixel.

Speed Timer tick in milliseconds.

With this Propertys we can figure out how the Gradient must be drawn. The GradientSizeInProcent is evaluated like this:

// get Gradient size n pixel from procent
decimal factor = (decimal) mainRect_.Width / 100;
GradientSize_ = (float) System.Math.Round( (decimal) 
         this.GradientSizeInProcent * factor);

Every time the timer ticks, the Position will increased by Step till current Position + Step is greater than the given mainRect_.Width. In this case Position is set back to 0. The Gradient updates to reflect changes.

//
pos_ = pos_ + stepSize_;
//
if (pos_ > mainRect_.Width)
{
    pos_ = 0;
}
PaintGardient();

Initalize needed Rectangle with mainRect_

//
bool useRightBrush = false;
bool useLeftBrush = false;
//
// init
RectangleF rectLeft = mainRect_;
RectangleF rectRight = mainRect_;
RectangleF rectRightFill = mainRect_;
RectangleF rectLeftFill = mainRect_;
RectangleF rectRightLeftEnd = mainRect_;
RectangleF rectRightRightEnd = mainRect_;

Get current position and evaluate Rectangles for each brush.


//    create Gradient rects        
rectLeft.Width =  gardientSize_;
rectLeft.X = pos_ - rectLeft.Width;
rectRight.X = mainRect_.X + pos_;
rectRight.Width = gardientSize_;
// create filler rects
rectLeftFill.Width = pos_ - gardientSize_;
rectRightFill.X = pos_ + gardientSize_;
rectRightFill.Width = mainRect_.Width - (pos_ + gardientSize_);
//
if ((pos_ + gardientSize_) > mainRect_.Width)
{
    rectRightRightEnd.X = - (mainRect_.Width - pos_);
    rectRightRightEnd.Width = gardientSize_;
    useRightBrush = true;
    //
    rectLeftFill.X = rectRightRightEnd.X + gardientSize_;
    rectLeftFill.Width -= rectRightRightEnd.X + gardientSize_;
}        
if (pos_ <= gardientSize_)
{
    useLeftBrush = true;
    //
    rectRightLeftEnd.X = (mainRect_.Width - gardientSize_) + pos_;
    rectRightLeftEnd.Width = gardientSize_;
    //    
    rectRightFill.X = rectRight.X + gardientSize_;
    rectRightFill.Width = rectRightLeftEnd.X - rectRightFill.X;

}

Get LinearGradientBrush based on evaluated Rectangles.

//create gardient brushes
Brush brushLeft = new LinearGradientBrush(rectLeft,color1_, color2_,0,true);
Brush brushRight = new LinearGradientBrush(rectRight,color2_, color1_,0,true);
Brush brushLeft1 = new LinearGradientBrush(rectRightLeftEnd,color1_, color2_,0,true);
Brush brushRight1 = new LinearGradientBrush(rectRightRightEnd,color2_, color1_,0,true);

Last but not least draw current position of the Gradient.

//
graphics_.FillRectangle(new SolidBrush(color1_),rectLeftFill);
//
graphics_.FillRectangle(brushLeft,rectLeft);
graphics_.FillRectangle(brushRight,rectRight);
//
graphics_.FillRectangle(new SolidBrush(color1_),rectRightFill);
//
if (useRightBrush)
{
    graphics_.FillRectangle(brushRight1,rectRightRightEnd);
}
            
//
if (useLeftBrush)
{
    graphics_.FillRectangle(brushLeft1,rectRightLeftEnd);
}