mirror of
https://github.com/xiaoqidun/ofdgo.git
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40 lines
1.7 KiB
Go
40 lines
1.7 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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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 threed
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import (
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"image"
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"math"
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)
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// viewImageBounds 计算采样器可能写入的像素范围，并在整数转换前裁至目标边界
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// 入参: source 原始像素边界, m 像素变换, target 目标边界
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// 返回: image.Rectangle 受影响的目标像素区域
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func viewImageBounds(source image.Rectangle, m [6]float64, target image.Rectangle) image.Rectangle {
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minX, minY, maxX, maxY := math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)
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for _, p := range [4]image.Point{source.Min, {X: source.Max.X, Y: source.Min.Y}, {X: source.Min.X, Y: source.Max.Y}, source.Max} {
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x := math.Floor(float64(m[0]*float64(p.X)) + float64(m[2]*float64(p.Y)) + m[4])
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y := math.Floor(float64(m[1]*float64(p.X)) + float64(m[3]*float64(p.Y)) + m[5])
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minX, minY = math.Min(minX, x), math.Min(minY, y)
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maxX, maxY = math.Max(maxX, x+1), math.Max(maxY, y+1)
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}
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minX, minY = math.Max(minX, float64(target.Min.X)), math.Max(minY, float64(target.Min.Y))
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maxX, maxY = math.Min(maxX, float64(target.Max.X)), math.Min(maxY, float64(target.Max.Y))
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if minX >= maxX || minY >= maxY {
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return image.Rectangle{}
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}
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return image.Rect(int(minX), int(minY), int(maxX), int(maxY))
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}
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