patterns_canvas 0.3.4

Draw patterns like stripes or dots on canvas elements or widgets.

Patterns

Flutter library to draw patterns like stripes or dots on Canvas elements or widgets.

patterns_canvas

A utility library that lets you paint Canvas shapes or widgets with patterns like dots, stripes, squares, etc.:

       

Simple Example

Inside your CustomPainter class's paint method, create a Pattern class with background (bgColor) and foreground (fgColor) colors and use one of its paintOn methods:

class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
  
    // Prepare a rectangle shape to draw the pattern on.
    final rect = Rect.fromLTWH(80, 50, 200, 100);
    
    // Create a Pattern object of diagonal stripes with the colors we want.
    final Pattern pattern = DiagonalStripesLight(bgColor: Colors.lightGreenAccent, fgColor: Colors.black);
    
    // Paint the pattern on the rectangle. 
    pattern.paintOnRect(canvas, size, rect);
    
  }
}

Results in this pattern drawn:

Pattern constructors and types:

You can construct a Pattern with three different ways:

1. Directly with a Pattern type constructor:

final Pattern p1 = DiagonalStripesLight(bgColor: Colors.yellowAccent, fgColor: Colors.black);

2. With the Pattern.fromValues factory constructor:

final Pattern p2 = Pattern.fromValues(patternType: PatternType.diagonalLight, bgColor: Colors.yellowAccent, fgColor: Colors.black);

3. From a String representation in the form of pattern_backgroundHex_foregroundHex:

final Pattern p3 = Pattern.fromString("diagonalLight_ffff00_000000");

Usage

Painting patterns on a Canvas shape:

• Create your Canvas element inside the paint function of your CustomPaint.
• Create a Pattern object with the desired type and colors.
• Use the corresponding paint method to draw the pattern on the object.

// In the build method of your screen:
...
body: Center(
    child: CustomPaint(
      size: const Size(double.infinity, double.infinity),
      painter: MyPainter(),
    ),
  ),
...

// In your CustomPainter:
class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
  
    final rect = Rect.fromLTWH(80, 50, 200, 100);
    DiagonalStripesLight(bgColor: Colors.lightGreenAccent, fgColor: Colors.black).paintOnRect(canvas, size, rect);
    
    final path = Path();
    path.moveTo(120, 200);
    path.lineTo(300, 280);
    path.quadraticBezierTo(20, 400, 40, 300);
    path.close();
    Crosshatch(bgColor: Colors.yellow, fgColor: Colors.black).paintOnPath(canvas, size, path);
    
  }
}

You can use the below methods to draw on Canvas shapes:

pattern.paintOnPath(canvas, size, path);
pattern.paintOnRect(canvas, size, rect);
pattern.paintOnRRect(canvas, size, rRect);
pattern.paintOnCircle(canvas, size, center, radius);

Check the Scale behavior setting section for more info on how the Pattern can be drawn.

Painting patterns on the whole Canvas:

As above, but you can use the paintOnCanvas method to draw the pattern on the whole Canvas:

TexturePattern(bgColor: Colors.white, fgColor: Colors.blueGrey).paintOnCanvas(canvas, size);

The result of the above paints:

Painting patterns on a Widget:

To draw patterns on a Widget, you need to:

• Wrap the Widget with a CustomPaint:

CustomPaint(
  painter: ContainerPatternPainter(),
  child: Container(
    width: 600,
    height: 200,
    child: Center(
      child: Text("Painting on a Container"),
    ),
  ),
),

• Inside your CustomPainter, create a Pattern and use its paintOnWidget method to paint with it:

class ContainerPatternPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    VerticalStripesThick(bgColor: Color(0xff0509050), fgColor: Color(0xfffdbf6f)).paintOnWidget(canvas, size);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}

Rectangular widgets, like Containers, Rows, Columns, IconButtons, etc. can be painted directly with the above method. For widgets that have a custom shape, like a BottomAppbar, you need to provide a different clipBehavior property, e.g. Clip.antiAlias, to make sure the pattern is clipped to the special shape. Check the second screen in the example app for more.

Patterns and settings

Available patterns

All Patterns require a background and foreground color on instantiation. The currently available patterns are:

Description	Class	PatternType enum
Horizontal Stripes Light	HorizontalStripesLight(Color bgColor, Color fgColor)	PatternType.horizontalLight
Horizontal Stripes Thick	HorizontalStripesThick(Color bgColor, Color fgColor)	PatternType.horizontalThick
Vertical Stripes Light	VerticalStripesLight(Color bgColor, Color fgColor)	PatternType.verticalLight
Vertical Stripes Thick	VerticalStripesThick(Color bgColor, Color fgColor)	PatternType.verticalThick
Diagonal Stripes Light	DiagonalStripesLight(Color bgColor, Color fgColor)	PatternType.diagonalLight
Diagonal Stripes Thick	DiagonalStripesThick(Color bgColor, Color fgColor)	PatternType.diagonalThick
Checkers	Checkers(Color bgColor, Color fgColor)	PatternType.checkers
Crosshatch	Crosshatch(Color bgColor, Color fgColor)	PatternType.crosshatch
Dots	Dots(Color bgColor, Color fgColor)	PatternType.dots
Raindrops	Raindrops(Color bgColor, Color fgColor)	PatternType.raindrops
Subtle Patch	SubtlePatch(Color bgColor, Color fgColor)	PatternType.subtlepatch
Texture	TexturePattern(Color bgColor, Color fgColor)	PatternType.texture

Scale behavior setting

All patterns are by default scaled to their container (patternScaleBehavior = PatternScaleBehavior.container). This means that, regardless of its size, a Rectangle will contain 40 diagonal stripes or 40 dots.

DiagonalStripesThick(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect1);
Dots(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect2);

You can change this behavior by providing a different argument to the paintOn method:

Pass patternScaleBehavior: PatternScaleBehavior.canvas to scale the pattern to the whole Canvas area. Now the Canvas will contain 40 diagonal stripes or 40 dots, so, a Rectangle will contain as many dots or stripes as it can fit:

DiagonalStripesThick(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect1, patternScaleBehavior: PatternScaleBehavior.canvas);
Dots(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect2, patternScaleBehavior: PatternScaleBehavior.canvas);

Pass patternScaleBehavior: PatternScaleBehavior.customRect and a customRect (e.g. a Rectangle with half the Canvas height) to further customize the Pattern size:

final Rect halfCanvas = Rect.fromLTWH(0, size.height / 2, size.width, size.height / 2); // a Rectangle with half the Canvas height.
DiagonalStripesThick(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect1, patternScaleBehavior: PatternScaleBehavior.customRect, customRect: halfCanvas );
Dots(bgColor: bgColor, fgColor: fgColor).paintOnRect(canvas, size, rect2, patternScaleBehavior: PatternScaleBehavior.customRect, customRect: halfCanvas );

It's also in the Roadmap to allow for selecting the number of Pattern features to use (e.g. draw only 5 diagonal stripes).