Kyle Isom
5993d20995
- SVG: strokes → SVG path elements with dashed/arrow support, coordinates scaled from 300 DPI to 72 DPI - JPG: rasterization at 300 DPI using Go image package, Bresenham line drawing with round pen circles - PDF: minimal PDF generation with raw operators, no external library - 6 tests: SVG output, dashed style, arrow heads, JPG magic bytes, PDF header, page size calculations Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
99 lines
2.1 KiB
Go
99 lines
2.1 KiB
Go
package render
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import (
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"bytes"
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"image"
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"image/color"
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"image/jpeg"
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"math"
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)
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// RenderJPG rasterizes a page's strokes at 300 DPI as JPEG.
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func RenderJPG(pageSize string, strokes []Stroke, quality int) ([]byte, error) {
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w, h := pageSizeCanonical(pageSize)
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img := image.NewRGBA(image.Rect(0, 0, w, h))
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// White background
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for y := 0; y < h; y++ {
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for x := 0; x < w; x++ {
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img.Set(x, y, color.White)
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}
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}
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// Draw strokes
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for _, s := range strokes {
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points := decodePoints(s.PointData)
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if len(points) < 4 {
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continue
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}
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c := argbToColor(s.Color)
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penRadius := float64(s.PenSize) / 2.0
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for i := 0; i < len(points)-3; i += 2 {
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x0, y0 := points[i], points[i+1]
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x1, y1 := points[i+2], points[i+3]
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drawLine(img, x0, y0, x1, y1, penRadius, c)
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}
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}
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var buf bytes.Buffer
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if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: quality}); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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func pageSizeCanonical(pageSize string) (int, int) {
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switch pageSize {
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case "LARGE":
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return 3300, 5100
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default:
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return 2550, 3300
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}
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}
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func argbToColor(argb int32) color.RGBA {
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return color.RGBA{
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R: uint8((argb >> 16) & 0xFF),
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G: uint8((argb >> 8) & 0xFF),
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B: uint8(argb & 0xFF),
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A: uint8((argb >> 24) & 0xFF),
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}
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}
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// drawLine draws a line with the given pen radius using Bresenham's.
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func drawLine(img *image.RGBA, x0, y0, x1, y1, radius float64, c color.RGBA) {
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dx := x1 - x0
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dy := y1 - y0
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dist := math.Sqrt(dx*dx + dy*dy)
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if dist < 1 {
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fillCircle(img, int(x0), int(y0), int(radius), c)
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return
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}
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steps := int(dist) + 1
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for i := 0; i <= steps; i++ {
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t := float64(i) / float64(steps)
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x := x0 + t*dx
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y := y0 + t*dy
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fillCircle(img, int(x), int(y), int(radius), c)
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}
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}
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func fillCircle(img *image.RGBA, cx, cy, r int, c color.RGBA) {
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if r < 1 {
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r = 1
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}
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bounds := img.Bounds()
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for dy := -r; dy <= r; dy++ {
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for dx := -r; dx <= r; dx++ {
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if dx*dx+dy*dy <= r*r {
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px, py := cx+dx, cy+dy
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if px >= bounds.Min.X && px < bounds.Max.X && py >= bounds.Min.Y && py < bounds.Max.Y {
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img.Set(px, py, c)
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}
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}
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}
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}
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}
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