Use of path gradient brush in gdi+

background

A path is a series of interconnected lines and curves , Consisting of many different types of points , Used to represent complex irregular figures , GraphicsPath Class represents .

Path gradient brush allows you to set a brush with a color gradient from the center to the boundary , You can set the color of the center point and the color of the boundary point .

Build path gradient brush

①． Use the path to build

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue,2);
  SolidBrush m_Brush(Color::Green);
  
  GraphicsPath m_Path;// Construct an empty path 
  m_Path.AddEllipse(30, 30, 180, 120);// Add ellipses 

  PathGradientBrush pathBrush(&m_Path);// Create brushes using paths 

  pathBrush.SetCenterColor(Color::Red);// Set center color 

  Color colors[] = {
     Color::Green ,Color::Green};
  int count = 1;
  pathBrush.SetSurroundColors(colors, &count);// Set the border color 

  graphics.FillEllipse(&pathBrush, 30, 30, 180, 120);
}

②． Use points to build

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue,2);
  SolidBrush m_Brush(Color::Green);
  
  Point points[] = {
     Point(30, 30), Point(180, 30), Point(180, 150), Point(30, 150) };

  PathGradientBrush pathBrush(points,4);// Use points to create brushes 

  pathBrush.SetCenterColor(Color::Red);// Set center color 

  Color colors[] = {
     Color::Green ,Color::Black,Color::Yellow,Color::Blue};
  int count = 4;
  pathBrush.SetSurroundColors(colors, &count);// Set the border color 

  graphics.FillRectangle(&pathBrush, 30, 30, 150, 120);
}

Focus and zoom

①． summary

Focus zoom is used to specify the internal track inside the master track , The center color fills the entire internal track range , Not just at the center point . You can call SetFocusScales Method to set Focus and zoom of a path gradient brush .

②． Set focus zoom

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue, 2);
  SolidBrush m_Brush(Color::Green);

  GraphicsPath m_Path;// Construct an empty path 
  m_Path.AddEllipse(30, 30, 180, 120);// Add ellipses 

  PathGradientBrush pathBrush(&m_Path);// Create brushes using paths 

  pathBrush.SetCenterColor(Color::Red);// Set center color 

  Color colors[] = {
     Color::Green ,Color::Green };
  int count = 1;
  pathBrush.SetSurroundColors(colors, &count);// Set the border color 

  pathBrush.SetFocusScales(0.3f, 0.3f);// Set focus zoom 

  graphics.FillEllipse(&pathBrush, 30, 30, 180, 120);
}

Interpolation color

①． summary

Using the interpolation color array, you can realize the gradient of multiple colors from the path boundary to the center point .

②． Use interpolated color gradients

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue, 2);
  SolidBrush m_Brush(Color::Green);

  GraphicsPath m_Path;// Construct an empty path 
  m_Path.AddRectangle(Rect(30,30,180,120));// Add rectangle 

  PathGradientBrush pathBrush(&m_Path);// Create brushes using paths 

  Color colors[] = {
    Color(255, 0, 128, 0),Color(255, 0, 255, 255),Color(255, 0, 0, 255) };
  REAL positions[] = {
    0.0f, 0.5f, 1.0f }; 

  pathBrush.SetInterpolationColors(colors, positions, 3);

  graphics.FillRectangle(&pathBrush, 30, 30, 180, 120);
}

Other parameter settings

①． Center point setting

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue, 2);
  SolidBrush m_Brush(Color::Green);

  GraphicsPath m_Path;// Construct an empty path 
  m_Path.AddEllipse(30, 30, 180, 120);// Add ellipses 

  PathGradientBrush pathBrush(&m_Path);// Create brushes using paths 

  pathBrush.SetCenterColor(Color::Red);// Set center color 

  Color colors[] = {
     Color::Green ,Color::Green };
  int count = 1;
  pathBrush.SetSurroundColors(colors, &count);// Set the border color 

  pathBrush.SetCenterPoint(Point(150, 75));

  graphics.FillEllipse(&pathBrush, 30, 30, 180, 120);
}

②． Use grayscale correction

void DemoGDI::DrawUser(HDC hdc)
{
    
  Graphics graphics(hdc);// structure  Graphics  object 
  Pen m_pen(Color::Blue, 2);
  SolidBrush m_Brush(Color::Green);

  GraphicsPath m_Path;// Construct an empty path 
  m_Path.AddEllipse(30, 30, 180, 120);// Add ellipses 

  PathGradientBrush pathBrush(&m_Path);// Create brushes using paths 

  pathBrush.SetCenterColor(Color::Red);// Set center color 

  Color colors[] = {
     Color::Green ,Color::Green };
  int count = 1;
  pathBrush.SetSurroundColors(colors, &count);// Set the border color 

  pathBrush.SetGammaCorrection(true);// Use grayscale correction 

  graphics.FillEllipse(&pathBrush, 30, 30, 180, 120);
}