feat(gallery): preload images

Reviewed-on: #2

README.md

@@ -91,4 +91,3 @@ To optimize images before uploading to Nextcloud:
 ```bash
 convert input.png -resize 3000 -quality 80 output.webp
 ```
-

internal/components/gallery/controller.go

@@ -2,6 +2,7 @@ package gallery
 
 import (
 	"context"
+	"log/slog"
 	"math"
 
 	"github.com/InfinityTools/go-binpack2d"
@@ -42,12 +43,17 @@ func (s *Service) GetGallery(ctx context.Context, width int) (gallery Gallery, e
 		return
 	}
 
-	packer := binpack2d.Create(width, 999999)
+	packer := binpack2d.Create(width, math.MaxInt)
 
 	for len(imgs) > 0 {
 		unused := make([]Image, 0, len(imgs))
 		for _, img := range imgs {
-			adjustImageSize(&img, 200)
+			adjustImageSizeStrictRatio(&img, 200)
+			if img.Height == 0 || img.Width == 0 {
+				slog.Warn("image has invalid size", "img", img)
+				continue
+			}
+
 			rect, ok := packer.Insert(img.Width, img.Height, binpack2d.RULE_BEST_SHORT_SIDE_FIT)
 			if !ok {
 				unused = append(unused, img)
@@ -70,17 +76,50 @@ func (s *Service) GetGallery(ctx context.Context, width int) (gallery Gallery, e
 	return
 }
 
-// adjustImageSize adjusts the image size so that the aspect ratio stays the same
+// getCleanRatio returns the simplified aspect ratio as (numerator, denominator).
-// but the image area is the given parameter.
+// It searches for the best fit within a denominator limit to account for rounding errors.
-func adjustImageSize(img *Image, area int) {
+func getCleanRatio(width, height int) (int, int) {
-	// Calculate the original aspect ratio (W / H)
+	targetRatio := float64(width) / float64(height)
-	aspectRatio := float64(img.Width) / float64(img.Height)
+	const maxDenominator = 100
 
-	// Calculate new height and width using the derived formulas
+	bestN, bestD := 0, 1
-	newHeight := math.Sqrt(float64(area) / aspectRatio)
+	minDiff := math.MaxFloat64
-	newWidth := newHeight * aspectRatio
 
-	// Round to the nearest integer to minimize precision loss
+	for d := 1; d <= maxDenominator; d++ {
-	img.Width = int(math.Round(newWidth))
+		// Calculate the closest numerator for this denominator
-	img.Height = int(math.Round(newHeight))
+		n := int(math.Round(float64(d) * targetRatio))
+
+		// Calculate the difference
+		currentRatio := float64(n) / float64(d)
+		diff := math.Abs(currentRatio - targetRatio)
+
+		// Keep track of the one with the smallest error
+		if diff < minDiff {
+			minDiff = diff
+			bestN, bestD = n, d
+		}
+	}
+
+	return bestN, bestD
+}
+
+func adjustImageSizeStrictRatio(img *Image, targetArea int) {
+	baseW, baseH := getCleanRatio(img.Width, img.Height)
+
+	baseArea := baseW * baseH
+
+	idealK := math.Sqrt(float64(targetArea) / float64(baseArea))
+
+	k := int(math.Floor(idealK))
+
+	if math.Abs(float64(k*k*baseArea-targetArea)) >
+		math.Abs(float64(int(math.Ceil(idealK))*int(math.Ceil(idealK))*baseArea-targetArea)) {
+		k = int(math.Ceil(idealK))
+	}
+
+	slog.Debug("adslkfj", "k", k, "idealK", idealK, "baseH", baseH, "baseW", baseW, "imgW", img.Width, "imgH", img.Height)
+
+	// 5. Apply the scaled dimensions (guarantees perfect aspect ratio)
+	img.Width = baseW * k
+	img.Height = baseH * k
 }

internal/components/gallery/image.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/internal/components/images"
 	"github.com/valkey-io/valkey-go"
 )
 
@@ -22,6 +23,10 @@ type Image struct {
 	Height int
 }
 
+func (i Image) URL() string {
+	return images.URLFromUID(i.UID)
+}
+
 const (
 	imagesKey = "gallery:images:list"
 	hashKey   = "gallery:images:hash"
@@ -45,7 +50,6 @@ func (s *Service) assembleImageList(ctx context.Context) error {
 	if err != nil {
 		return fmt.Errorf("could not read contents of %s: %w", s.cfg.Path, err)
 	}
-	slog.Debug("loaded files", "files", files)
 
 	savedHash, _ := s.cache.Do(ctx, s.cache.B().Get().Key(hashKey).Build()).AsBytes()
 
@@ -77,10 +81,19 @@ func (s *Service) assembleImageList(ctx context.Context) error {
 			continue
 		}
 
+		w := img.Bounds().Dx()
+		h := img.Bounds().Dy()
+
+		// FIX 2: Defensive check to guard against unreadable/corrupted image boundaries
+		if w <= 0 || h <= 0 {
+			slog.Warn("skipping image with zero or negative dimensions", "path", imagePath, "w", w, "h", h)
+			continue
+		}
+
 		imgs = append(imgs, Image{
 			UID:    uid,
-			Width:  img.Bounds().Dx(),
+			Width:  w,
-			Height: img.Bounds().Dy(),
+			Height: h,
 		})
 	}
 

internal/components/images/helpers.go

@@ -33,6 +33,11 @@ func UIDFromPath(path string) (uid string, err error) {
 
 func URLFromPath(path string) (url string, err error) {
 	uid, err := UIDFromPath(path)
+	url = URLFromUID(uid)
+	return
+}
+
+func URLFromUID(uid string) (url string) {
 	url = "/images/" + uid
 	return
 }

internal/handlers/restgallery/controller.go

@@ -1,12 +1,16 @@
 package restgallery
 
 import (
+	"fmt"
 	"log/slog"
 	"net/http"
 
+	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/internal/pkg/templer"
 	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/web/pages"
 )
 
+const preloadCount = 6
+
 func (h *Handler) gallery(w http.ResponseWriter, r *http.Request) {
 	imgs, err := h.srv.GetGallerySet(r.Context())
 	if err != nil {
@@ -14,5 +18,14 @@ func (h *Handler) gallery(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	h.r.Render(r.Context(), w, r, pages.GallerySet(imgs))
+	ctx := r.Context()
+	for i, image := range imgs.LG.Images {
+		if i > preloadCount {
+			break
+		}
+		slog.Info("preloading images", "img", image.UID)
+		ctx = templer.AppendHeader(ctx, fmt.Sprintf(`<link rel="preload" href="%s" as="image" />`, image.URL()))
+	}
+
+	h.r.Render(ctx, w, r, pages.GallerySet(imgs))
 }