NOTE - This project is deprecated. See pebble-fctx for the latest.
This is a fork of pebble-hacks/gpath-bezier. It adds support for subpixel accurate rendering of filled paths. Additionally, on color Pebble devices, antialiasing is supported.
The UP button now switches between the native GPath rendering and the new FPath rendering for comparison. Also, the rotation rate has been slowed considerably to make it easier to see just how effective the subpixel accuracy is at smoothing both the shape and the animation.
Written against the PebbleSDK v3.0-beta10
The interesting parts are derived from the following excellent resources:
Perspective Texture Mapping Game Developer Magazine Chris Hecker Copyright (c) 1995-1997 Chris Hecker. All rights reserved. http://chrishecker.com/Miscellaneous_Technical_Articles
Scanline edge-flag algorithm for antialiasing EG UK Theory and Practice of Computer Graphics (2007) Kiia Kallio Copyright (c) 2005-2007 Kiia Kallio kkallio@uiah.fi http://mlab.uiah.fi/~kkallio/antialiasing/
The Edge Flag Algorithm--A Fill Method for Raster Scan Displays IEEE Transactions On Computers, Volume C-30, No. 1, January 1981. Bryan D. Ackland and Neil H. Weste
The original README for pebble-hacks/gpath-bezier follows:
Drawing complex paths requires a lot of manual work on Pebble. You can do this
efficiently and quickly using a Pebble-optimized GPath algorithm and Bezier
curves.
This library introduces the GPathBuilder API that allows you to
programmatically contruct GPath objects by specifying start and end points for
a curve. The builder than adds intermetiary points to make the curve as smooth
as is practical.
You can draw the path shown above using only the GPathBuilder code below:
// Create GPathBuilder object
GPathBuilder *builder = gpath_builder_create(MAX_POINTS);
// Move to the starting point of the GPath
gpath_builder_move_to_point(builder, GPoint(0, -60));
// Create curve
gpath_builder_curve_to_point(builder, GPoint(60, 0), GPoint(35, -60), GPoint(60, -35));
// Create straight line
gpath_builder_line_to_point(builder, GPoint(-60, 0));
// Create another curve
gpath_builder_curve_to_point(builder, GPoint(0, 60), GPoint(-60, 35), GPoint(-35, 60));
// Create another straight line
gpath_builder_line_to_point(builder, GPoint(0, -60));
// Create GPath object out of our GPathBuilder object
s_path = gpath_builder_create_path(builder);
// Destroy GPathBuilder object
gpath_builder_destroy(builder);
// Get window bounds
GRect bounds = layer_get_bounds(window_get_root_layer(window));
// Move newly created GPath to the center of the screen
gpath_move_to(s_path, GPoint((int16_t)(bounds.size.w/2), (int16_t)(bounds.size.h/2)));
You can learn more about Bezier curves by reading the Pebble Developers blog post Bezier Curves and GPaths on Pebble.