Canvas#
Canvas is a control for drawing arbitrary graphics using a set of primitives or "shapes" such as line, arc, path and text.
Example:
Basic Canvas
Inherits: LayoutControl
Properties
-
content(Control | None) –The content of this canvas.
-
resize_interval(Number) –Sampling interval in milliseconds for
on_resizeevent. -
shapes(list[Shape]) –A list of shapes to draw on this canvas.
Events
-
on_resize(EventHandler[CanvasResizeEvent] | None) –Called when the size of this canvas has changed.
Methods
-
capture–Captures the current visual state of the canvas.
-
clear_capture–Clears the previously captured canvas image.
-
get_capture–Retrieves the most recent canvas capture as PNG bytes.
Examples#
Smiling face#
import math
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
stroke_paint = ft.Paint(stroke_width=2, style=ft.PaintingStyle.STROKE)
fill_paint = ft.Paint(style=ft.PaintingStyle.FILL)
page.add(
ft.SafeArea(
content=cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Circle(x=100, y=100, radius=50, paint=stroke_paint),
cv.Circle(x=80, y=90, radius=10, paint=stroke_paint),
cv.Circle(x=84, y=87, radius=5, paint=fill_paint),
cv.Circle(x=120, y=90, radius=10, paint=stroke_paint),
cv.Circle(x=124, y=87, radius=5, paint=fill_paint),
cv.Arc(
x=70,
y=95,
width=60,
height=40,
start_angle=0,
sweep_angle=math.pi,
paint=stroke_paint,
),
],
)
)
)
if __name__ == "__main__":
ft.run(main)
Flet logo#
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
page.theme_mode = ft.ThemeMode.LIGHT
page.add(
ft.SafeArea(
content=cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Path(
elements=[
cv.Path.MoveTo(x=25, y=125),
cv.Path.QuadraticTo(cp1x=50, cp1y=25, x=135, y=35, w=0.35),
cv.Path.QuadraticTo(cp1x=75, cp1y=115, x=135, y=215, w=0.6),
cv.Path.QuadraticTo(cp1x=50, cp1y=225, x=25, y=125, w=0.35),
],
paint=ft.Paint(
stroke_width=2,
style=ft.PaintingStyle.FILL,
color=ft.Colors.PINK_400,
),
),
cv.Path(
elements=[
cv.Path.MoveTo(x=85, y=125),
cv.Path.QuadraticTo(cp1x=120, cp1y=85, x=165, y=75, w=0.5),
cv.Path.QuadraticTo(
cp1x=120, cp1y=115, x=165, y=175, w=0.3
),
cv.Path.QuadraticTo(cp1x=120, cp1y=165, x=85, y=125, w=0.5),
],
paint=ft.Paint(
stroke_width=2,
style=ft.PaintingStyle.FILL,
color=ft.Colors.with_opacity(0.5, ft.Colors.BLUE_400),
),
),
],
)
)
)
if __name__ == "__main__":
ft.run(main)
Triangles#
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
page.add(
ft.SafeArea(
content=cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Path(
paint=ft.Paint(style=ft.PaintingStyle.FILL),
elements=[
cv.Path.MoveTo(x=25, y=25),
cv.Path.LineTo(x=105, y=25),
cv.Path.LineTo(x=25, y=105),
],
),
cv.Path(
paint=ft.Paint(stroke_width=2, style=ft.PaintingStyle.STROKE),
elements=[
cv.Path.MoveTo(x=125, y=125),
cv.Path.LineTo(x=125, y=45),
cv.Path.LineTo(x=45, y=125),
cv.Path.Close(),
],
),
],
)
)
)
if __name__ == "__main__":
ft.run(main)
Bezier curves#
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
cp = cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Path(
paint=ft.Paint(stroke_width=2, style=ft.PaintingStyle.STROKE),
elements=[
cv.Path.MoveTo(x=75, y=25),
cv.Path.QuadraticTo(cp1x=25, cp1y=25, x=25, y=62.5),
cv.Path.QuadraticTo(cp1x=25, cp1y=100, x=50, y=100),
cv.Path.QuadraticTo(cp1x=50, cp1y=120, x=30, y=125),
cv.Path.QuadraticTo(cp1x=60, cp1y=120, x=65, y=100),
cv.Path.QuadraticTo(cp1x=125, cp1y=100, x=125, y=62.5),
cv.Path.QuadraticTo(cp1x=125, cp1y=25, x=75, y=25),
],
),
cv.Path(
elements=[
cv.Path.SubPath(
x=100,
y=100,
elements=[
cv.Path.MoveTo(x=75, y=40),
cv.Path.CubicTo(
cp1x=75, cp1y=37, cp2x=70, cp2y=25, x=50, y=25
),
cv.Path.CubicTo(
cp1x=20, cp1y=25, cp2x=20, cp2y=62.5, x=20, y=62.5
),
cv.Path.CubicTo(
cp1x=20, cp1y=80, cp2x=40, cp2y=102, x=75, y=120
),
cv.Path.CubicTo(
cp1x=110, cp1y=102, cp2x=130, cp2y=80, x=130, y=62.5
),
cv.Path.CubicTo(
cp1x=130, cp1y=62.5, cp2x=130, cp2y=25, x=100, y=25
),
cv.Path.CubicTo(
cp1x=85, cp1y=25, cp2x=75, cp2y=37, x=75, y=40
),
],
)
],
paint=ft.Paint(
style=ft.PaintingStyle.FILL,
gradient=ft.PaintRadialGradient(
center=ft.Offset(150, 150),
radius=50,
colors=[ft.Colors.PINK_100, ft.Colors.PINK],
),
),
),
],
)
page.add(ft.SafeArea(content=cp))
if __name__ == "__main__":
ft.run(main)
Text#
import math
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
page.add(
ft.SafeArea(
content=cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Text(x=0, y=0, value="Just a text"),
cv.Circle(
x=200, y=100, radius=2, paint=ft.Paint(color=ft.Colors.RED)
),
cv.Text(
x=200,
y=100,
style=ft.TextStyle(weight=ft.FontWeight.BOLD, size=30),
alignment=ft.Alignment.TOP_CENTER,
rotate=math.pi * 0.15,
value="Rotated",
spans=[
ft.TextSpan(
text="around top_center",
style=ft.TextStyle(
italic=True, color=ft.Colors.GREEN, size=20
),
)
],
),
cv.Circle(
x=400, y=100, radius=2, paint=ft.Paint(color=ft.Colors.RED)
),
cv.Text(
x=400,
y=100,
value="Rotated around top_left",
style=ft.TextStyle(size=20),
alignment=ft.Alignment.TOP_LEFT,
rotate=math.pi * -0.15,
),
cv.Circle(
x=600, y=200, radius=2, paint=ft.Paint(color=ft.Colors.RED)
),
cv.Text(
x=600,
y=200,
value="Rotated around center",
style=ft.TextStyle(size=20),
alignment=ft.Alignment.CENTER,
rotate=math.pi / 2,
),
cv.Text(
x=300,
y=400,
value=(
"Limited to max_width and right-aligned.\n"
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, "
"sed do eiusmod tempor incididunt ut labore et dolore "
"magna aliqua. Ut enim ad minim veniam, quis nostrud "
"exercitation "
"ullamco laboris nisi ut aliquip ex ea commodo consequat."
),
text_align=ft.TextAlign.RIGHT,
max_width=400,
),
cv.Text(
x=200,
y=200,
value="WOW!",
style=ft.TextStyle(
weight=ft.FontWeight.BOLD,
size=100,
foreground=ft.Paint(
color=ft.Colors.PINK,
stroke_width=6,
style=ft.PaintingStyle.STROKE,
stroke_join=ft.StrokeJoin.ROUND,
stroke_cap=ft.StrokeCap.ROUND,
),
),
),
cv.Text(
x=200,
y=200,
value="WOW!",
style=ft.TextStyle(
weight=ft.FontWeight.BOLD,
size=100,
foreground=ft.Paint(
gradient=ft.PaintLinearGradient(
begin=(200, 200),
end=(300, 300),
colors=[ft.Colors.YELLOW, ft.Colors.RED],
),
stroke_join=ft.StrokeJoin.ROUND,
stroke_cap=ft.StrokeCap.ROUND,
),
),
),
],
)
)
)
if __name__ == "__main__":
ft.run(main)
Free-hand drawing with image capture#
from dataclasses import dataclass
import flet as ft
import flet.canvas as cv
MAX_SHAPES_PER_CAPTURE = 30
@dataclass
class State:
x: float = 0
y: float = 0
shapes_count: int = 1
state = State()
def main(page: ft.Page):
page.title = "Canvas Example"
file_picker = ft.FilePicker()
def handle_pan_start(e: ft.DragStartEvent):
state.x = e.local_position.x
state.y = e.local_position.y
async def handle_pan_update(e: ft.DragUpdateEvent):
# ft.context.disable_auto_update()
canvas.shapes.append(
cv.Line(
x1=state.x,
y1=state.y,
x2=e.local_position.x,
y2=e.local_position.y,
paint=ft.Paint(stroke_width=3),
)
)
canvas.update()
state.shapes_count += 1
if state.shapes_count == MAX_SHAPES_PER_CAPTURE:
await canvas.capture()
canvas.shapes.clear()
canvas.update()
state.shapes_count = 0
state.x = e.local_position.x
state.y = e.local_position.y
canvas = cv.Canvas(
expand=False,
shapes=[
cv.Fill(ft.Paint(color=ft.Colors.WHITE)),
],
content=ft.GestureDetector(
on_pan_start=handle_pan_start,
on_pan_update=handle_pan_update,
drag_interval=10,
),
)
async def save_image():
await canvas.capture()
capture = await canvas.get_capture()
if capture:
file_path = await file_picker.save_file(
file_name="flet_picture.png", src_bytes=capture
)
if file_path and page.platform in [
ft.PagePlatform.MACOS,
ft.PagePlatform.WINDOWS,
ft.PagePlatform.LINUX,
]:
with open(file_path, "wb") as f:
f.write(capture)
page.add(
ft.SafeArea(
expand=True,
content=ft.Column(
controls=[
ft.Button("Save image", on_click=save_image),
ft.Container(
border_radius=5,
border=ft.Border.all(2),
bgcolor=ft.Colors.WHITE,
width=float("inf"),
expand=True,
content=canvas,
),
]
),
),
)
if __name__ == "__main__":
ft.run(main)
Gradients#
import math
import flet as ft
import flet.canvas as cv
def main(page: ft.Page):
page.add(
ft.SafeArea(
content=cv.Canvas(
width=float("inf"),
expand=True,
shapes=[
cv.Rect(
x=10,
y=10,
width=100,
height=100,
border_radius=5,
paint=ft.Paint(
style=ft.PaintingStyle.FILL,
gradient=ft.PaintLinearGradient(
begin=(0, 10),
end=(100, 50),
colors=[ft.Colors.BLUE, ft.Colors.YELLOW],
),
),
),
cv.Circle(
x=60,
y=170,
radius=50,
paint=ft.Paint(
style=ft.PaintingStyle.FILL,
gradient=ft.PaintRadialGradient(
radius=50,
center=(60, 170),
colors=[ft.Colors.YELLOW, ft.Colors.BLUE],
),
),
),
cv.Path(
elements=[
cv.Path.Arc(
x=10,
y=230,
width=100,
height=100,
start_angle=3 * math.pi / 4,
sweep_angle=3 * math.pi / 2,
),
],
paint=ft.Paint(
stroke_width=15,
stroke_join=ft.StrokeJoin.ROUND,
style=ft.PaintingStyle.STROKE,
gradient=ft.PaintSweepGradient(
start_angle=0,
end_angle=math.pi * 2,
rotation=3 * math.pi / 4,
center=(60, 280),
colors=[ft.Colors.YELLOW, ft.Colors.PURPLE],
color_stops=[0.0, 1.0],
),
),
),
],
)
)
)
if __name__ == "__main__":
ft.run(main)
Properties#
class-attribute
instance-attribute
#
content: Control | None = None
The content of this canvas.
class-attribute
instance-attribute
#
resize_interval: Number = 10
Sampling interval in milliseconds for on_resize event.
Setting to 0 calls on_resize immediately
on every change.
class-attribute
instance-attribute
#
A list of shapes to draw on this canvas.
Events#
class-attribute
instance-attribute
#
on_resize: EventHandler[CanvasResizeEvent] | None = None
Called when the size of this canvas has changed.
Methods#
async
#
capture(pixel_ratio: Number | None = None)
Captures the current visual state of the canvas.
The captured image is stored internally and will be rendered as a background beneath all subsequently drawn shapes.
Parameters:
-
pixel_ratio(Number | None, default:None) –The pixel density multiplier to use when rendering the capture.
1.0means 1 device pixel per logical pixel (no scaling). Values greater than1.0produce higher-resolution captures. IfNone, the device's default pixel ratio is used.
async
#
Clears the previously captured canvas image.
After clearing, no background will be rendered from a prior capture.