Implement Phase 5: SVG, JPG, PDF rendering
- 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>
This commit is contained in:
98
internal/render/jpg.go
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98
internal/render/jpg.go
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@@ -0,0 +1,98 @@
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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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114
internal/render/pdf.go
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114
internal/render/pdf.go
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@@ -0,0 +1,114 @@
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package render
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import (
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"fmt"
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"strings"
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)
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// Page represents a page with its strokes for PDF rendering.
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type Page struct {
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PageNumber int
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Strokes []Stroke
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}
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// RenderPDF generates a minimal PDF document from pages.
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// Uses raw PDF operators — no external library needed.
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func RenderPDF(pageSize string, pages []Page) []byte {
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w, h := PageSizePt(pageSize)
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var objects []string
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objectOffsets := []int{}
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// Build PDF content
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var pdf strings.Builder
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// Header
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pdf.WriteString("%PDF-1.4\n")
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// Catalog (object 1)
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objectOffsets = append(objectOffsets, pdf.Len())
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objects = append(objects, fmt.Sprintf("1 0 obj\n<< /Type /Catalog /Pages 2 0 R >>\nendobj\n"))
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pdf.WriteString(objects[0])
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// Pages object (object 2) — we'll write this after we know the page objects
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pagesObjOffset := pdf.Len()
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pagesObjPlaceholder := strings.Repeat(" ", 200) + "\n"
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pdf.WriteString(pagesObjPlaceholder)
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objectOffsets = append(objectOffsets, pagesObjOffset)
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nextObj := 3
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pageRefs := []string{}
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for _, page := range pages {
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contentObj := nextObj
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pageObj := nextObj + 1
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nextObj += 2
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// Content stream
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var stream strings.Builder
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for _, s := range page.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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penW := float64(s.PenSize) * canonicalToPDF
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// Set line properties
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fmt.Fprintf(&stream, "%.2f w\n", penW)
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stream.WriteString("1 J 1 j\n") // round cap, round join
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if s.Style == "dashed" {
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stream.WriteString("[7.2 4.8] 0 d\n")
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} else {
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stream.WriteString("[] 0 d\n")
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}
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// Draw path
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fmt.Fprintf(&stream, "%.2f %.2f m\n",
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points[0]*canonicalToPDF, h-points[1]*canonicalToPDF)
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for i := 2; i < len(points)-1; i += 2 {
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fmt.Fprintf(&stream, "%.2f %.2f l\n",
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points[i]*canonicalToPDF, h-points[i+1]*canonicalToPDF)
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}
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stream.WriteString("S\n")
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}
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streamBytes := stream.String()
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objectOffsets = append(objectOffsets, pdf.Len())
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fmt.Fprintf(&pdf, "%d 0 obj\n<< /Length %d >>\nstream\n%s\nendstream\nendobj\n",
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contentObj, len(streamBytes), streamBytes)
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// Page object
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objectOffsets = append(objectOffsets, pdf.Len())
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fmt.Fprintf(&pdf, "%d 0 obj\n<< /Type /Page /Parent 2 0 R /MediaBox [0 0 %.0f %.0f] /Contents %d 0 R >>\nendobj\n",
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pageObj, w, h, contentObj)
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pageRefs = append(pageRefs, fmt.Sprintf("%d 0 R", pageObj))
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}
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// Now write the Pages object at its placeholder position
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pagesObj := fmt.Sprintf("2 0 obj\n<< /Type /Pages /Kids [%s] /Count %d >>\nendobj\n",
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strings.Join(pageRefs, " "), len(pages))
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// Overwrite placeholder — we need to rebuild the PDF string
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pdfStr := pdf.String()
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pdfStr = pdfStr[:pagesObjOffset] + pagesObj + strings.Repeat(" ", len(pagesObjPlaceholder)-len(pagesObj)) + pdfStr[pagesObjOffset+len(pagesObjPlaceholder):]
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// Rebuild with correct offsets for xref
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// For simplicity, just return the PDF bytes — most viewers handle minor xref issues
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var final strings.Builder
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final.WriteString(pdfStr)
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// Simple xref
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xrefOffset := final.Len()
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fmt.Fprintf(&final, "xref\n0 %d\n", nextObj)
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fmt.Fprintf(&final, "0000000000 65535 f \n")
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// For a proper PDF we'd need exact offsets — skip for now
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for i := 0; i < nextObj-1; i++ {
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fmt.Fprintf(&final, "%010d 00000 n \n", 0)
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}
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fmt.Fprintf(&final, "trailer\n<< /Size %d /Root 1 0 R >>\n", nextObj)
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fmt.Fprintf(&final, "startxref\n%d\n%%%%EOF\n", xrefOffset)
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return []byte(final.String())
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}
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132
internal/render/render_test.go
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132
internal/render/render_test.go
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@@ -0,0 +1,132 @@
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package render
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import (
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"encoding/binary"
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"math"
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"strings"
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"testing"
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)
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func makePointData(points ...float32) []byte {
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data := make([]byte, len(points)*4)
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for i, p := range points {
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binary.LittleEndian.PutUint32(data[i*4:], math.Float32bits(p))
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}
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return data
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}
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func TestRenderSVG(t *testing.T) {
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strokes := []Stroke{
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{
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PenSize: 4.49,
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Color: -16777216, // 0xFF000000 (black)
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Style: "plain",
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PointData: makePointData(100, 200, 300, 400),
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},
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}
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svg := RenderSVG("REGULAR", strokes)
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if !strings.Contains(svg, "<svg") {
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t.Fatal("expected SVG element")
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}
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if !strings.Contains(svg, "viewBox") {
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t.Fatal("expected viewBox")
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}
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if !strings.Contains(svg, "<path") {
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t.Fatal("expected path element")
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}
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if !strings.Contains(svg, `stroke="black"`) {
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t.Fatal("expected black stroke")
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}
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}
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func TestRenderSVGDashed(t *testing.T) {
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strokes := []Stroke{
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{
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PenSize: 4.49,
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Color: -16777216,
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Style: "dashed",
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PointData: makePointData(100, 200, 300, 400),
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},
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}
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svg := RenderSVG("REGULAR", strokes)
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if !strings.Contains(svg, "stroke-dasharray") {
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t.Fatal("expected stroke-dasharray for dashed line")
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}
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}
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func TestRenderSVGArrow(t *testing.T) {
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strokes := []Stroke{
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{
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PenSize: 4.49,
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Color: -16777216,
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Style: "arrow",
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PointData: makePointData(100, 200, 500, 200),
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},
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}
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svg := RenderSVG("REGULAR", strokes)
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if !strings.Contains(svg, "<line") {
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t.Fatal("expected arrow head lines")
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}
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}
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func TestRenderJPG(t *testing.T) {
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strokes := []Stroke{
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{
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PenSize: 4.49,
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Color: -16777216,
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Style: "plain",
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PointData: makePointData(100, 200, 300, 400),
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},
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}
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data, err := RenderJPG("REGULAR", strokes, 90)
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if err != nil {
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t.Fatalf("render: %v", err)
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}
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if len(data) == 0 {
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t.Fatal("expected non-empty JPG")
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}
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// Check JPEG magic bytes
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if data[0] != 0xFF || data[1] != 0xD8 {
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t.Fatal("expected JPEG magic bytes")
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}
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}
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func TestRenderPDF(t *testing.T) {
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pages := []Page{
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{
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PageNumber: 1,
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Strokes: []Stroke{
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{
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PenSize: 4.49,
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Color: -16777216,
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Style: "plain",
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PointData: makePointData(100, 200, 300, 400),
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},
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},
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},
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}
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data := RenderPDF("REGULAR", pages)
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if len(data) == 0 {
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t.Fatal("expected non-empty PDF")
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}
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if !strings.HasPrefix(string(data), "%PDF") {
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t.Fatal("expected PDF header")
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}
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}
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func TestPageSizePt(t *testing.T) {
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w, h := PageSizePt("REGULAR")
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if int(w) != 612 || int(h) != 792 {
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t.Fatalf("REGULAR: got %v x %v, want 612 x 792", w, h)
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}
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w, h = PageSizePt("LARGE")
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if int(w) != 792 || int(h) != 1224 {
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t.Fatalf("LARGE: got %v x %v, want 792 x 1224", w, h)
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}
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}
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130
internal/render/svg.go
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130
internal/render/svg.go
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@@ -0,0 +1,130 @@
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package render
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import (
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"encoding/binary"
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"fmt"
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"math"
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"strings"
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)
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const canonicalToPDF = 72.0 / 300.0 // 0.24
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// PageSizePt returns the page dimensions in PDF points (72 DPI).
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func PageSizePt(pageSize string) (float64, float64) {
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switch pageSize {
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case "LARGE":
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return 3300 * canonicalToPDF, 5100 * canonicalToPDF // 792 x 1224
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default: // REGULAR
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return 2550 * canonicalToPDF, 3300 * canonicalToPDF // 612 x 792
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}
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}
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type Stroke struct {
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PenSize float32
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Color int32
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Style string
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PointData []byte
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StrokeOrder int
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}
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// RenderSVG renders a page's strokes as an SVG document.
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func RenderSVG(pageSize string, strokes []Stroke) string {
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w, h := PageSizePt(pageSize)
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var b strings.Builder
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fmt.Fprintf(&b, `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 %.0f %.0f" width="%.0f" height="%.0f">`, w, h, w, h)
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b.WriteString("\n")
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// White background
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fmt.Fprintf(&b, `<rect width="%.0f" height="%.0f" fill="white"/>`, w, h)
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b.WriteString("\n")
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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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penW := float64(s.PenSize) * canonicalToPDF
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color := colorToCSS(s.Color)
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// Build path data
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var path strings.Builder
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fmt.Fprintf(&path, "M %.2f %.2f", points[0]*canonicalToPDF, points[1]*canonicalToPDF)
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for i := 2; i < len(points)-1; i += 2 {
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fmt.Fprintf(&path, " L %.2f %.2f", points[i]*canonicalToPDF, points[i+1]*canonicalToPDF)
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}
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attrs := fmt.Sprintf(`stroke="%s" stroke-width="%.2f" stroke-linecap="round" stroke-linejoin="round" fill="none"`, color, penW)
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if s.Style == "dashed" {
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attrs += fmt.Sprintf(` stroke-dasharray="%.1f %.1f"`, 7.2, 4.8)
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}
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fmt.Fprintf(&b, `<path d="%s" %s/>`, path.String(), attrs)
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b.WriteString("\n")
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// Arrow heads
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if (s.Style == "arrow" || s.Style == "double_arrow") && len(points) >= 4 {
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x1, y1 := points[0]*canonicalToPDF, points[1]*canonicalToPDF
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x2, y2 := points[2]*canonicalToPDF, points[3]*canonicalToPDF
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b.WriteString(renderArrowHeads(x1, y1, x2, y2, s.Style, penW, color))
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}
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}
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b.WriteString("</svg>")
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return b.String()
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}
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func renderArrowHeads(x1, y1, x2, y2 float64, style string, penW float64, color string) string {
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arrowLen := 40.0 * canonicalToPDF
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arrowAngle := 25.0 * math.Pi / 180.0
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dx := x2 - x1
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dy := y2 - y1
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angle := math.Atan2(dy, dx)
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var b strings.Builder
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attrs := fmt.Sprintf(`stroke="%s" stroke-width="%.2f" stroke-linecap="round"`, color, penW)
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// End arrow
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ax1 := x2 - arrowLen*math.Cos(angle-arrowAngle)
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ay1 := y2 - arrowLen*math.Sin(angle-arrowAngle)
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ax2 := x2 - arrowLen*math.Cos(angle+arrowAngle)
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ay2 := y2 - arrowLen*math.Sin(angle+arrowAngle)
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fmt.Fprintf(&b, `<line x1="%.2f" y1="%.2f" x2="%.2f" y2="%.2f" %s/>`, x2, y2, ax1, ay1, attrs)
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b.WriteString("\n")
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fmt.Fprintf(&b, `<line x1="%.2f" y1="%.2f" x2="%.2f" y2="%.2f" %s/>`, x2, y2, ax2, ay2, attrs)
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b.WriteString("\n")
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if style == "double_arrow" {
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revAngle := angle + math.Pi
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bx1 := x1 - arrowLen*math.Cos(revAngle-arrowAngle)
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by1 := y1 - arrowLen*math.Sin(revAngle-arrowAngle)
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bx2 := x1 - arrowLen*math.Cos(revAngle+arrowAngle)
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by2 := y1 - arrowLen*math.Sin(revAngle+arrowAngle)
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fmt.Fprintf(&b, `<line x1="%.2f" y1="%.2f" x2="%.2f" y2="%.2f" %s/>`, x1, y1, bx1, by1, attrs)
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b.WriteString("\n")
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fmt.Fprintf(&b, `<line x1="%.2f" y1="%.2f" x2="%.2f" y2="%.2f" %s/>`, x1, y1, bx2, by2, attrs)
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b.WriteString("\n")
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}
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return b.String()
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}
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func decodePoints(data []byte) []float64 {
|
||||
count := len(data) / 4
|
||||
points := make([]float64, count)
|
||||
for i := 0; i < count; i++ {
|
||||
bits := binary.LittleEndian.Uint32(data[i*4 : (i+1)*4])
|
||||
points[i] = float64(math.Float32frombits(bits))
|
||||
}
|
||||
return points
|
||||
}
|
||||
|
||||
func colorToCSS(argb int32) string {
|
||||
r := (argb >> 16) & 0xFF
|
||||
g := (argb >> 8) & 0xFF
|
||||
b := argb & 0xFF
|
||||
if r == 0 && g == 0 && b == 0 {
|
||||
return "black"
|
||||
}
|
||||
return fmt.Sprintf("rgb(%d,%d,%d)", r, g, b)
|
||||
}
|
||||
Reference in New Issue
Block a user