neco-view2d

日本語

A minimal 2D camera / viewport transform for moving between world space and canvas space. Useful for image viewers, 2D editors, and any UI where the user pans and zooms over a plane.

Coordinate transform

The transform maps between world space and canvas space (screen / CSS pixels).

View2d stores center_x, center_y, and view_size, where view_size is the visible world-space height on the canvas.

• canvas_to_world(cx, cy, canvas_width, canvas_height) converts a canvas point to world coordinates.
• world_to_canvas(wx, wy, canvas_width, canvas_height) converts a world point to canvas coordinates.
• pan(dx, dy, canvas_height) shifts the view by a pixel delta scaled by view_size / canvas_height.
• zoom_at(delta, canvas_x, canvas_y, canvas_width, canvas_height) keeps the world point under the cursor fixed while changing view_size.

view_size is clamped to stay positive. Smaller view_size means more zoom.

Usage

use neco_view2d::View2d;

let mut view = View2d::default();

// pan by a pixel delta on a 600px-tall canvas
view.pan(50.0, 30.0, 600.0);

// zoom in around canvas center
view.zoom_at(120.0, 400.0, 300.0, 800.0, 600.0);

// coordinate conversion
let (cx, cy) = view.world_to_canvas(100.0, 200.0, 800.0, 600.0);
let (wx, wy) = view.canvas_to_world(cx, cy, 800.0, 600.0);

API

Optional features

License

MIT