84 lines
2.6 KiB
Go
84 lines
2.6 KiB
Go
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package svg
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import (
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"fmt"
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"html"
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"strings"
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"b612.me/astro/moon"
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)
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// writeOccultationGreatestTimeContours 绘制地方掩甚时刻等值线及其 HH:MM 标注。
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func writeOccultationGreatestTimeContours(
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b *strings.Builder,
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contours []moon.OccultationGreatestTimeContour,
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layout starOccultationSVGLayout,
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options StarOccultationSVGOptions,
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placer *occultationLabelPlacer,
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) {
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if len(contours) == 0 {
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return
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}
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type isochroneLabel struct {
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x, y float64
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text string
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}
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labels := make([]isochroneLabel, 0, len(contours))
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for _, contour := range contours {
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for _, segment := range contour.Segments {
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writeStarOccultationGeoLine(b, segment, layout,
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occultationLineStyle{className: "greatest-time-isoline", color: "#1f6fb2", strokeWidth: 1.1})
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}
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text := contour.Time.In(options.Location).Format("15:04")
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if x, y, ok := occultationGreatestTimeIsolineLabelPlacement(contour, text, layout, placer); ok {
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labels = append(labels, isochroneLabel{x: x, y: y, text: text})
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}
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}
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for _, label := range labels {
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fmt.Fprintf(b, `<text class="greatest-time-isoline-label" x="%.3f" y="%.3f" fill="#1a5c96" stroke="#ffffff" stroke-width="2.6" paint-order="stroke" font-family="Arial, sans-serif" font-size="9" font-weight="700" text-anchor="middle">%s</text>`,
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label.x, label.y, html.EscapeString(label.text))
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}
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}
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// occultationGreatestTimeIsolineLabelPlacement 在最长的支路上取首个未被其它标签占用的标注点。
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func occultationGreatestTimeIsolineLabelPlacement(
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contour moon.OccultationGreatestTimeContour,
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text string,
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layout starOccultationSVGLayout,
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placer *occultationLabelPlacer,
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) (float64, float64, bool) {
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longest := -1
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for index, segment := range contour.Segments {
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if longest < 0 || len(segment) > len(contour.Segments[longest]) {
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longest = index
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}
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}
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if longest < 0 {
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return 0, 0, false
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}
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segment := contour.Segments[longest]
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frame := layout.mapFrame()
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middle := len(segment) / 2
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for offset := 0; offset <= middle; offset++ {
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for _, index := range []int{middle + offset, middle - offset} {
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if index < 0 || index >= len(segment) {
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continue
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}
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point := segment[index]
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x, y, visible := frame.Project(point.Longitude, point.Latitude)
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if !visible ||
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x < frame.X+30 || x > frame.X+frame.Width-30 ||
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y < frame.Y+18 || y > frame.Y+frame.Height-18 {
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continue
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}
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// 优先压在等时线上方，其次下方；两者都被占用就换下一个候选点。
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for _, baseline := range []float64{y - 6, y + 13} {
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if placer.place(x, baseline, "middle", text, 9, 2) {
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return x, baseline, true
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}
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}
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}
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}
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return 0, 0, false
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}
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