ebiten/internal/colormcache/cache.go

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// Copyright 2020 The Ebiten Authors
//
// 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.
package colormcache
import (
"image/color"
"math"
"github.com/hajimehoshi/ebiten"
)
var (
monotonicClock int64
)
func now() int64 {
monotonicClock++
return monotonicClock
}
const (
cacheLimit = 512 // This is an arbitrary number.
)
type colorMCacheKey uint32
type colorMCacheEntry struct {
m ebiten.ColorM
atime int64
}
var (
colorMCache = map[colorMCacheKey]*colorMCacheEntry{}
emptyColorM ebiten.ColorM
)
func init() {
emptyColorM.Scale(0, 0, 0, 0)
}
func ColorToColorM(clr color.Color) ebiten.ColorM {
// RGBA() is in [0 - 0xffff]. Adjust them in [0 - 0xff].
cr, cg, cb, ca := clr.RGBA()
cr /= 0x101
cg /= 0x101
cb /= 0x101
ca /= 0x101
if ca == 0 {
return emptyColorM
}
key := colorMCacheKey(uint32(cr) | (uint32(cg) << 8) | (uint32(cb) << 16) | (uint32(ca) << 24))
e, ok := colorMCache[key]
if ok {
e.atime = now()
return e.m
}
if len(colorMCache) > cacheLimit {
oldest := int64(math.MaxInt64)
oldestKey := colorMCacheKey(0)
for key, c := range colorMCache {
if c.atime < oldest {
oldestKey = key
oldest = c.atime
}
}
delete(colorMCache, oldestKey)
}
cm := ebiten.ColorM{}
rf := float64(cr) / float64(ca)
gf := float64(cg) / float64(ca)
bf := float64(cb) / float64(ca)
af := float64(ca) / 0xff
cm.Scale(rf, gf, bf, af)
e = &colorMCacheEntry{
m: cm,
atime: now(),
}
colorMCache[key] = e
return e.m
}