patterns_canvas 0.3.5
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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 Pub Version #

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 = DiagonalStripesThick(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);
  1. With the Pattern.fromValues factory constructor:
final Pattern p2 = Pattern.fromValues(patternType: PatternType.diagonalLight, bgColor: Colors.yellowAccent, fgColor: Colors.black);
  1. From a String representation in the form of patternType_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:

DescriptionClassPatternType enum
Horizontal Stripes LightHorizontalStripesLight(Color bgColor, Color fgColor)PatternType.horizontalLight
Horizontal Stripes ThickHorizontalStripesThick(Color bgColor, Color fgColor)PatternType.horizontalThick
Vertical Stripes LightVerticalStripesLight(Color bgColor, Color fgColor)PatternType.verticalLight
Vertical Stripes ThickVerticalStripesThick(Color bgColor, Color fgColor)PatternType.verticalThick
Diagonal Stripes LightDiagonalStripesLight(Color bgColor, Color fgColor)PatternType.diagonalLight
Diagonal Stripes ThickDiagonalStripesThick(Color bgColor, Color fgColor)PatternType.diagonalThick
CheckersCheckers(Color bgColor, Color fgColor)PatternType.checkers
CrosshatchCrosshatch(Color bgColor, Color fgColor)PatternType.crosshatch
DotsDots(Color bgColor, Color fgColor)PatternType.dots
RaindropsRaindrops(Color bgColor, Color fgColor)PatternType.raindrops
Subtle PatchSubtlePatch(Color bgColor, Color fgColor)PatternType.subtlepatch
TextureTexturePattern(Color bgColor, Color fgColor)PatternType.texture

Setting the number of pattern features to draw #

You can pass a featuresCount argument when creating a Pattern, to set how many features, e.g. how many stripes, you want to be drawn.

DiagonalStripesThick(bgColor: bgColor, fgColor: fgColor, featuresCount: 40).paintOnRect(canvas, size, rect1);
Dots(bgColor: bgColor, fgColor: fgColor, featuresCount: 5).paintOnRect(canvas, size, rect2);

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 15 diagonal stripes or 10 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 15 diagonal stripes or 10 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 );

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Publisher

whidev.com

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

Repository (GitHub)
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Documentation

API reference

License

MIT (LICENSE)

Dependencies

flutter

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