130 lines
3.2 KiB
Rust
130 lines
3.2 KiB
Rust
// Copyright 2006 The Android Open Source Project
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// Copyright 2020 Yevhenii Reizner
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//
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Skia uses fixed points pretty chaotically, therefore we cannot use
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// strongly typed wrappers. Which is unfortunate.
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use tiny_skia_path::SaturateCast;
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use crate::math::{bound, left_shift, left_shift64};
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/// A 26.6 fixed point.
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pub type FDot6 = i32;
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/// A 24.8 fixed point.
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pub type FDot8 = i32;
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/// A 16.16 fixed point.
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pub type FDot16 = i32;
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pub mod fdot6 {
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use super::*;
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use core::convert::TryFrom;
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pub const ONE: FDot6 = 64;
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pub fn from_i32(n: i32) -> FDot6 {
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debug_assert!(n as i16 as i32 == n);
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n << 6
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}
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pub fn from_f32(n: f32) -> FDot6 {
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(n * 64.0) as i32
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}
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pub fn floor(n: FDot6) -> FDot6 {
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n >> 6
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}
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pub fn ceil(n: FDot6) -> FDot6 {
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(n + 63) >> 6
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}
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pub fn round(n: FDot6) -> FDot6 {
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(n + 32) >> 6
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}
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pub fn to_fdot16(n: FDot6) -> FDot16 {
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debug_assert!((left_shift(n, 10) >> 10) == n);
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left_shift(n, 10)
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}
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pub fn div(a: FDot6, b: FDot6) -> FDot16 {
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debug_assert_ne!(b, 0);
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if i16::try_from(a).is_ok() {
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left_shift(a, 16) / b
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} else {
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fdot16::div(a, b)
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}
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}
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pub fn can_convert_to_fdot16(n: FDot6) -> bool {
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let max_dot6 = core::i32::MAX >> (16 - 6);
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n.abs() <= max_dot6
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}
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pub fn small_scale(value: u8, dot6: FDot6) -> u8 {
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debug_assert!(dot6 as u32 <= 64);
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((value as i32 * dot6) >> 6) as u8
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}
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}
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pub mod fdot8 {
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use super::*;
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// Extracted from SkScan_Antihair.cpp
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pub fn from_fdot16(x: FDot16) -> FDot8 {
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(x + 0x80) >> 8
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}
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}
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pub mod fdot16 {
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use super::*;
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pub const HALF: FDot16 = (1 << 16) / 2;
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pub const ONE: FDot16 = 1 << 16;
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// `from_f32` seems to lack a rounding step. For all fixed-point
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// values, this version is as accurate as possible for (fixed -> float -> fixed). Rounding reduces
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// accuracy if the intermediate floats are in the range that only holds integers (adding 0.5 to an
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// odd integer then snaps to nearest even). Using double for the rounding math gives maximum
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// accuracy for (float -> fixed -> float), but that's usually overkill.
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pub fn from_f32(x: f32) -> FDot16 {
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i32::saturate_from(x * ONE as f32)
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}
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pub fn floor_to_i32(x: FDot16) -> i32 {
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x >> 16
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}
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pub fn ceil_to_i32(x: FDot16) -> i32 {
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(x + ONE - 1) >> 16
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}
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pub fn round_to_i32(x: FDot16) -> i32 {
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(x + HALF) >> 16
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}
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// The divide may exceed 32 bits. Clamp to a signed 32 bit result.
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pub fn mul(a: FDot16, b: FDot16) -> FDot16 {
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((i64::from(a) * i64::from(b)) >> 16) as FDot16
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}
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// The divide may exceed 32 bits. Clamp to a signed 32 bit result.
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pub fn div(numer: FDot6, denom: FDot6) -> FDot16 {
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let v = left_shift64(numer as i64, 16) / denom as i64;
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let n = bound(i32::MIN as i64, v, i32::MAX as i64);
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n as i32
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}
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pub fn fast_div(a: FDot6, b: FDot6) -> FDot16 {
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debug_assert!((left_shift(a, 16) >> 16) == a);
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debug_assert!(b != 0);
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left_shift(a, 16) / b
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}
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}
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