mirror of
https://github.com/hajimehoshi/ebiten.git
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75 lines
2.1 KiB
Go
75 lines
2.1 KiB
Go
// Copyright 2017 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ebitenutil
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import (
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"image/color"
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"math"
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"github.com/hajimehoshi/ebiten"
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)
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var (
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emptyImage *ebiten.Image
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)
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func init() {
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// Filter must be 'nearest' filter.
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// Linear filtering would make edges blurred.
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emptyImage, _ = ebiten.NewImage(16, 16, ebiten.FilterNearest)
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_ = emptyImage.Fill(color.White)
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}
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func colorScale(clr color.Color) (rf, gf, bf, af float64) {
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r, g, b, a := clr.RGBA()
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if a == 0 {
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return 0, 0, 0, 0
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}
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rf = float64(r) / float64(a)
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gf = float64(g) / float64(a)
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bf = float64(b) / float64(a)
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af = float64(a) / 0xffff
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return
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}
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// DrawLine draws a line segment on the given destination dst.
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//
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// DrawLine is intended to be used mainly for debugging or prototyping purpose.
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func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
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ew, eh := emptyImage.Size()
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length := math.Hypot(x2-x1, y2-y1)
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op := &ebiten.DrawImageOptions{}
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op.GeoM.Scale(length/float64(ew), 1/float64(eh))
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op.GeoM.Rotate(math.Atan2(y2-y1, x2-x1))
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op.GeoM.Translate(x1, y1)
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op.ColorM.Scale(colorScale(clr))
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_ = dst.DrawImage(emptyImage, op)
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}
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// DrawRect draws a rectangle on the given destination dst.
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//
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// DrawRect is intended to be used mainly for debugging or prototyping purpose.
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func DrawRect(dst *ebiten.Image, x, y, width, height float64, clr color.Color) {
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ew, eh := emptyImage.Size()
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op := &ebiten.DrawImageOptions{}
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op.GeoM.Scale(width/float64(ew), height/float64(eh))
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op.GeoM.Translate(x, y)
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op.ColorM.Scale(colorScale(clr))
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_ = dst.DrawImage(emptyImage, op)
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}
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