From c678c7aa454b576aa11fb0f7c896b95b7153a53b Mon Sep 17 00:00:00 2001
From: schreifuchs <kontakt@schreifuchs.ch>
Date: Mon, 8 Jun 2026 11:18:44 +0200
Subject: [PATCH] fix(gallery): use correct aspect ratios

---
 README.md                                 |  1 -
 internal/components/gallery/controller.go | 65 ++++++++++++++++++-----
 internal/components/gallery/image.go      | 14 +++--
 3 files changed, 63 insertions(+), 17 deletions(-)

diff --git a/README.md b/README.md
index c9bf8f7..9d155e1 100644
--- a/README.md
+++ b/README.md
@@ -91,4 +91,3 @@ To optimize images before uploading to Nextcloud:
 ```bash
 convert input.png -resize 3000 -quality 80 output.webp
 ```
-
diff --git a/internal/components/gallery/controller.go b/internal/components/gallery/controller.go
index 90adfe8..1dd8d16 100644
--- a/internal/components/gallery/controller.go
+++ b/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
-// but the image area is the given parameter.
-func adjustImageSize(img *Image, area int) {
-	// Calculate the original aspect ratio (W / H)
-	aspectRatio := float64(img.Width) / float64(img.Height)
+// getCleanRatio returns the simplified aspect ratio as (numerator, denominator).
+// It searches for the best fit within a denominator limit to account for rounding errors.
+func getCleanRatio(width, height int) (int, int) {
+	targetRatio := float64(width) / float64(height)
+	const maxDenominator = 100
 
-	// Calculate new height and width using the derived formulas
-	newHeight := math.Sqrt(float64(area) / aspectRatio)
-	newWidth := newHeight * aspectRatio
+	bestN, bestD := 0, 1
+	minDiff := math.MaxFloat64
 
-	// Round to the nearest integer to minimize precision loss
-	img.Width = int(math.Round(newWidth))
-	img.Height = int(math.Round(newHeight))
+	for d := 1; d <= maxDenominator; d++ {
+		// Calculate the closest numerator for this denominator
+		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
 }
diff --git a/internal/components/gallery/image.go b/internal/components/gallery/image.go
index 5a48548..c249d7a 100644
--- a/internal/components/gallery/image.go
+++ b/internal/components/gallery/image.go
@@ -45,7 +45,6 @@ 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 +76,19 @@ 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(),
-			Height: img.Bounds().Dy(),
+			Width:  w,
+			Height: h,
 		})
 	}