Have you noticed the transform parameter in the Container and Transform widgets, that let you move, rotate, resize and flip?

This package is a helper math class that makes it easy to create Matrix4 transformations.

Example:

// Rotates the Container 45 degrees and then
// translates 25 pixels to the right. 
Container(
   transform:
     Matrix4Transform()
       .rotateDegrees(45, origin: Offset(25, 25))
       .translate(x: 25)
       .matrix4,
   child: ...
);

To see it in action, run the example in the example tab.

Matrix4Transform is immutable (in contrast, Matrix4 is mutable).

First create a Matrix4Transform:

Matrix4Transform();

Then call the methods to transform it. For example:

Matrix4Transform()
   .scale(1.5)
   .upRight(35)
   .rotate(pi/2);

In the end, call matrix4:

Matrix4 myMatrix 
   = Matrix4Transform()
     .scale(1.5)
     .upRight(35)
     .rotate(pi/2)
     .matrix4;                        

Note: The transformations will be applied in order, and their order may change the end result.

If you already have a matrix4 and want to further transform it, you can use the from constructor:

Matrix4 myMatrix = ...;

var myTransform = Matrix4Transform.from(myMatrix);

• rotate(double angleRadians, {Offset origin})
• rotateDegrees(double angleDegrees, {Offset origin})
• rotateByCenterDegrees(double angleDegrees, Size size)
• rotateByCenter(_toRadians(angleDegrees), size)
• translate({double x = 0, double y = 0})
• translateOriginalCoordinates({double x = 0, double y = 0})
• scale(double factor, {Offset origin})
• scaleBy({double x = 1, double y = 1, Offset origin})
• scaleHorizontally(double factor)
• scaleVertically(double factor)
• translateOffset(Offset offset)
• up(double distance)
• down(double distance)
• right(double distance)
• left(double distance)
• direction(double directionRadians, double distance)
• directionDegrees(double directionDegrees, double distance)
• upRight(double distance)
• upLeft(double distance)
• downRight(double distance)
• downLeft(double distance)
• flipDiagonally({Offset origin})
• flipHorizontally({Offset origin})
• flipVertically({Offset origin})

And, of course:

• Matrix4 toMatrix4

A Matrix4TransformTween is provided in this package, and can be used in animations.

A Matrix4Transform can be used to animate:

• AlignPositioned or AnimatedAlignPositioned widgets from the AlignPositioned package, that accept a Matrix4Transform directly. The center of rotation/scale can be defined by their alignment parameter.

• Any widget that accepts a Matrix4 transformation parameter, like Container, or AnimatedContainer. Note: Since Matrix4Tween will not animate linearly as you'd expect, it's possible that the intermediary transformations will be "strange", although the start and end should be correct.

Special thanks to Martin Kamleithner and Simon Lightfoot.

The Flutter packages I've authored:

• async_redux
• fast_immutable_collections
• provider_for_redux
• i18n_extension
• align_positioned
• network_to_file_image
• image_pixels
• matrix4_transform
• back_button_interceptor
• indexed_list_view
• animated_size_and_fade
• assorted_layout_widgets
• weak_map
• themed

My Medium Articles:

• Async Redux: Flutter’s non-boilerplate version of Redux ( versions: Português)
• i18n_extension ( versions: Português)
• Flutter: The Advanced Layout Rule Even Beginners Must Know ( versions: русский)
• The New Way to create Themes in your Flutter App

My article in the official Flutter documentation:

• Understanding constraints

---
Marcelo Glasberg:
https://github.com/marcglasberg
https://twitter.com/glasbergmarcelo
https://stackoverflow.com/users/3411681/marcg
https://medium.com/@marcglasberg