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Render display math environments in rich mode

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This commit is contained in:
corrado.mulas
2026-10-04 12:13:28 +02:00
parent 3abaf71920
commit 7fefe2ee50
5 changed files with 303 additions and 71 deletions
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45
internal/render/render.go
View File

@@ -9,9 +9,7 @@ import (
"errors"
"fmt"
"image"
"image/color"
"image/draw"
"image/jpeg"
_ "image/jpeg"
_ "image/png"
"math"
"os"
@@ -386,12 +384,10 @@ func (r *Renderer) renderRaster(ctx context.Context, workdir string, dpi int, pd
}
// renderThumbnail creates the dedicated small JPEG used only by Telegram's
// inline-result picker. It centers the aspect-correct preview on a square
// canvas because some clients force inline thumbnails into a square slot.
// Supplying the rectangular preview directly makes those clients stretch it.
// inline-result picker. It preserves the formula's aspect ratio and only
// shrinks oversized previews; short expressions are never enlarged.
func (r *Renderer) renderThumbnail(ctx context.Context, workdir string, dpi int, pdfPath, outPath string) error {
base := strings.TrimSuffix(outPath, filepath.Ext(outPath)) + "-source"
sourcePath := base + ".jpg"
base := strings.TrimSuffix(outPath, filepath.Ext(outPath))
args := []string{
"-jpeg", "-jpegopt", "quality=82,progressive=n,optimize=y",
"-r", strconv.Itoa(dpi), "-singlefile", "-f", "1", "-l", "1",
@@ -399,7 +395,7 @@ func (r *Renderer) renderThumbnail(ctx context.Context, workdir string, dpi int,
if err := r.run(ctx, workdir, r.Pdftoppm, append(args, pdfPath, base)...); err != nil {
return fmt.Errorf("render inline thumbnail: %w", err)
}
width, height, err := imageSize(sourcePath)
width, height, err := imageSize(outPath)
if err != nil {
return fmt.Errorf("inspect inline thumbnail: %w", err)
}
@@ -410,7 +406,7 @@ func (r *Renderer) renderThumbnail(ctx context.Context, workdir string, dpi int,
if err := r.run(ctx, workdir, r.Pdftoppm, append(scaledArgs, pdfPath, base)...); err != nil {
return fmt.Errorf("scale inline thumbnail: %w", err)
}
width, height, err = imageSize(sourcePath)
width, height, err = imageSize(outPath)
if err != nil {
return fmt.Errorf("inspect scaled inline thumbnail: %w", err)
}
@@ -418,38 +414,9 @@ func (r *Renderer) renderThumbnail(ctx context.Context, workdir string, dpi int,
if width > inlineThumbnailSide || height > inlineThumbnailSide {
return fmt.Errorf("inline thumbnail is unexpectedly large: %dx%d", width, height)
}
sourceData, err := os.ReadFile(sourcePath)
if err != nil {
return fmt.Errorf("read inline thumbnail: %w", err)
}
source, err := jpeg.Decode(bytes.NewReader(sourceData))
if err != nil {
return fmt.Errorf("decode inline thumbnail: %w", err)
}
thumbnail := squareThumbnail(source)
var encoded bytes.Buffer
if err := jpeg.Encode(&encoded, thumbnail, &jpeg.Options{Quality: 82}); err != nil {
return fmt.Errorf("encode inline thumbnail: %w", err)
}
if err := os.WriteFile(outPath, encoded.Bytes(), 0o600); err != nil {
return fmt.Errorf("write inline thumbnail: %w", err)
}
return nil
}
// squareThumbnail pads rather than stretches the already-scaled preview.
func squareThumbnail(source image.Image) *image.RGBA {
canvas := image.NewRGBA(image.Rect(0, 0, inlineThumbnailSide, inlineThumbnailSide))
draw.Draw(canvas, canvas.Bounds(), image.NewUniform(color.White), image.Point{}, draw.Src)
bounds := source.Bounds()
x := (inlineThumbnailSide - bounds.Dx()) / 2
y := (inlineThumbnailSide - bounds.Dy()) / 2
target := image.Rect(x, y, x+bounds.Dx(), y+bounds.Dy())
draw.Draw(canvas, target, source, bounds.Min, draw.Src)
return canvas
}
func imageSize(path string) (int, int, error) {
file, err := os.Open(path)
if err != nil {

29
internal/render/render_test.go
View File

@@ -4,8 +4,6 @@ import (
"bytes"
"context"
"image"
"image/color"
"image/draw"
_ "image/png"
"os/exec"
"strings"
@@ -123,8 +121,8 @@ func TestRenderIntegration(t *testing.T) {
if err != nil {
t.Fatalf("decode thumbnail size: %v", err)
}
if thumbWidth != inlineThumbnailSide || thumbHeight != inlineThumbnailSide {
t.Errorf("thumbnail is %dx%d, want a %dx%d padded square", thumbWidth, thumbHeight, inlineThumbnailSide, inlineThumbnailSide)
if thumbWidth > inlineThumbnailSide || thumbHeight > inlineThumbnailSide {
t.Errorf("thumbnail is %dx%d, want no side beyond %d", thumbWidth, thumbHeight, inlineThumbnailSide)
}
linked, err := r.Render(ctx, "", `\hypertarget{details}{Details}\par\hyperlink{details}{Go to details}`, 150)
@@ -136,29 +134,6 @@ func TestRenderIntegration(t *testing.T) {
}
}
func TestSquareThumbnailPadsWithoutStretching(t *testing.T) {
source := image.NewRGBA(image.Rect(0, 0, 160, 80))
draw.Draw(source, source.Bounds(), image.NewUniform(color.Black), image.Point{}, draw.Src)
thumbnail := squareThumbnail(source)
if thumbnail.Bounds() != image.Rect(0, 0, inlineThumbnailSide, inlineThumbnailSide) {
t.Fatalf("thumbnail bounds = %v", thumbnail.Bounds())
}
for _, sample := range []struct {
point image.Point
want color.RGBA
}{
{image.Pt(160, 119), color.RGBA{255, 255, 255, 255}},
{image.Pt(160, 120), color.RGBA{0, 0, 0, 255}},
{image.Pt(79, 160), color.RGBA{255, 255, 255, 255}},
{image.Pt(80, 160), color.RGBA{0, 0, 0, 255}},
} {
if got := thumbnail.RGBAAt(sample.point.X, sample.point.Y); got != sample.want {
t.Errorf("pixel at %v = %v, want %v", sample.point, got, sample.want)
}
}
}
func pngSizeBytes(data []byte) (int, int, error) {
return imageSizeBytes(data)
}