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// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! An antialiased rasterizer for quadratic Beziers
use std::cmp::min;
use accumulate::accumulate;
use geom::Point;
// TODO: sort out crate structure. Right now we want this when compiling raster as a binary,
// but need it commented out when compiling showttf
//mod geom;
pub struct Raster {
w: usize,
h: usize,
a: Vec<f32>,
}
// TODO: is there a faster way? (investigate whether approx recip is good enough)
fn recip(x: f32) -> f32 {
x.recip()
}
impl Raster {
pub fn new(w: usize, h: usize) -> Raster {
Raster {
w: w,
h: h,
a: vec![0.0; w * h + 4],
}
}
pub fn draw_line(&mut self, p0: &Point, p1: &Point) {
//println!("draw_line {} {}", p0, p1);
if p0.y == p1.y {
return;
}
let (dir, p0, p1) = if p0.y < p1.y {
(1.0, p0, p1)
} else {
(-1.0, p1, p0)
};
let dxdy = (p1.x - p0.x) / (p1.y - p0.y);
let mut x = p0.x;
let y0 = p0.y as usize; // note: implicit max of 0 because usize (TODO: really true?)
if p0.y < 0.0 {
x -= p0.y * dxdy;
}
for y in y0..min(self.h, p1.y.ceil() as usize) {
let linestart = y * self.w;
let dy = ((y + 1) as f32).min(p1.y) - (y as f32).max(p0.y);
let xnext = x + dxdy * dy;
let d = dy * dir;
let (x0, x1) = if x < xnext { (x, xnext) } else { (xnext, x) };
let x0floor = x0.floor();
let x0i = x0floor as i32;
let x1ceil = x1.ceil();
let x1i = x1ceil as i32;
if x1i <= x0i + 1 {
let xmf = 0.5 * (x + xnext) - x0floor;
self.a[linestart + x0i as usize] += d - d * xmf;
self.a[linestart + (x0i + 1) as usize] += d * xmf;
} else {
let s = recip(x1 - x0);
let x0f = x0 - x0floor;
let a0 = 0.5 * s * (1.0 - x0f) * (1.0 - x0f);
let x1f = x1 - x1ceil + 1.0;
let am = 0.5 * s * x1f * x1f;
self.a[linestart + x0i as usize] += d * a0;
if x1i == x0i + 2 {
self.a[linestart + (x0i + 1) as usize] += d * (1.0 - a0 - am);
} else {
let a1 = s * (1.5 - x0f);
self.a[linestart + (x0i + 1) as usize] += d * (a1 - a0);
for xi in x0i + 2..x1i - 1 {
self.a[linestart + xi as usize] += d * s;
}
let a2 = a1 + (x1i - x0i - 3) as f32 * s;
self.a[linestart + (x1i - 1) as usize] += d * (1.0 - a2 - am);
}
self.a[linestart + x1i as usize] += d * am;
}
x = xnext;
}
}
pub fn draw_quad(&mut self, p0: &Point, p1: &Point, p2: &Point) {
//println!("draw_quad {} {} {}", p0, p1, p2);
let devx = p0.x - 2.0 * p1.x + p2.x;
let devy = p0.y - 2.0 * p1.y + p2.y;
let devsq = devx * devx + devy * devy;
if devsq < 0.333 {
self.draw_line(p0, p2);
return;
}
let tol = 3.0;
let n = 1 + (tol * (devx * devx + devy * devy)).sqrt().sqrt().floor() as usize;
//println!("n = {}", n);
let mut p = *p0;
let nrecip = recip(n as f32);
let mut t = 0.0;
for _i in 0..n - 1 {
t += nrecip;
let pn = Point::lerp(t, &Point::lerp(t, p0, p1), &Point::lerp(t, p1, p2));
self.draw_line(&p, &pn);
p = pn;
}
self.draw_line(&p, p2);
}
/*
fn get_bitmap_fancy(&self) -> Vec<u8> {
let mut acc = 0.0;
// This would translate really well to SIMD
self.a[0..self.w * self.h].iter().map(|&a| {
acc += a;
(255.0 * acc.abs().min(1.0)) as u8
//(255.5 * (0.5 + 0.4 * acc)) as u8
}).collect()
}
*/
pub fn get_bitmap(&self) -> Vec<u8> {
accumulate(&self.a[0..self.w * self.h])
}
}
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