mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 15:06:46 +08:00
104 lines
3.7 KiB
Go
104 lines
3.7 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 ofdgo
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import (
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"fmt"
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"image"
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"math"
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)
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// viewLayers 按ECMA-363第9.5.4节依次绘制背景层或覆盖层
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// 入参: layers 按后至前排列的纹理层
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// 返回: error 参数、资源、预算或取消错误
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func (r *u3dRender) viewLayers(layers []U3DViewLayer) error {
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for _, layer := range layers {
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if err := r.ctx.Err(); err != nil {
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return err
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}
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for _, value := range [...]float32{layer.Blend, layer.Rotation, layer.Location[0], layer.Location[1], layer.Scale[0], layer.Scale[1]} {
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if !finite(float64(value)) {
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return fmt.Errorf("invalid U3D view layer values")
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}
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}
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texture, err := r.texture(layer.Texture)
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if err != nil {
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return err
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}
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blend := min(1, max(0, float64(layer.Blend)))
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if blend == 0 || layer.Scale[0] == 0 || layer.Scale[1] == 0 {
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continue
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}
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sin, cos := math.Sincos(float64(layer.Rotation))
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x, y := float64(layer.Location[0]), float64(layer.Location[1])
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if r.view.Attributes&1 != 0 {
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x *= float64(r.output.Rect.Dx())
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y *= float64(r.output.Rect.Dy())
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}
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sx, sy := float64(layer.Scale[0]), float64(layer.Scale[1])
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rx, ry := float64(layer.Registration[0]), float64(layer.Registration[1])
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m := RasterMatrix{cos * sx, -sin * sx, sin * sy, cos * sy, x - cos*sx*rx - sin*sy*ry, y + sin*sx*rx - cos*sy*ry}
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bounds := rasterImageBounds(texture.Bounds(), m, r.output.Bounds())
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for py := bounds.Min.Y; py < bounds.Max.Y; py++ {
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for px := bounds.Min.X; px < bounds.Max.X; px++ {
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if px%4096 == 0 || px == bounds.Min.X {
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if err := r.ctx.Err(); err != nil {
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return err
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}
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}
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cx, cy := float64(px)+.5, float64(py)+.5
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if cx < r.viewport[0] || cy < r.viewport[1] || cx >= r.viewport[0]+r.viewport[2] || cy >= r.viewport[1]+r.viewport[3] {
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continue
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}
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dx, dy := cx-x, cy-y
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u, v := (cos*dx-sin*dy)/sx+rx, (sin*dx+cos*dy)/sy+ry
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if u < 0 || v < 0 || u >= float64(texture.Rect.Dx()) || v >= float64(texture.Rect.Dy()) {
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continue
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}
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value := u3dTextureSample(texture, u, v)
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pixel := &r.frame[py*r.output.Rect.Dx()+px]
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alpha := value[3] * blend
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for i := range pixel.color {
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pixel.color[i] = value[i]*blend + pixel.color[i]*(1-alpha)
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}
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}
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}
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}
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return r.ctx.Err()
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}
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// u3dTextureSample 在像素中心进行双线性采样，使用预乘颜色避免透明边缘色晕
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// 入参: texture 纹理, x 横向像素坐标, y 纵向像素坐标
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// 返回: [4]float64 预乘颜色及透明度
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func u3dTextureSample(texture *image.NRGBA64, x, y float64) [4]float64 {
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x, y = x-.5, y-.5
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x0, y0 := int(math.Floor(x)), int(math.Floor(y))
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fx, fy := x-float64(x0), y-float64(y0)
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wx, wy := [2]float64{1 - fx, fx}, [2]float64{1 - fy, fy}
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var result [4]float64
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for row := range 2 {
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for col := range 2 {
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weight := wx[col] * wy[row]
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c := texture.NRGBA64At(min(max(0, x0+col), texture.Rect.Max.X-1), min(max(0, y0+row), texture.Rect.Max.Y-1))
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alpha := float64(c.A) / 65535
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result[0] += float64(c.R) / 65535 * alpha * weight
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result[1] += float64(c.G) / 65535 * alpha * weight
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result[2] += float64(c.B) / 65535 * alpha * weight
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result[3] += alpha * weight
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}
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}
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return result
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}
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