fix: Slide-Modus auf Gruppen-basiertes Sliding umgestellt

Vorher: split(/\s+/) zerlegte alles in Einzelwoerter, verlor die
Spaltenstruktur (3+ Spaces zwischen Gruppen). Woerter stauten sich links.

Jetzt: split(/\s{3,}/) erhält Gruppen wie im Cluster-Modus. Jede Gruppe
wird als Einheit von links nach rechts geschoben bis Tinte gefunden.
Breite = max(gemessene Textbreite, tatsaechliche Tintenbreite).
fontRatio=1.0, kein Wort geht verloren.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

admin-lehrer/components/ocr-overlay/useSlideWordPositions.ts

@@ -11,20 +11,17 @@ export interface WordPosition {
 /**
  * "Slide from left" positioning algorithm.
  *
- * Takes ALL recognised words per cell and slides them left-to-right across
- * the row's dark-pixel projection until each word "locks" onto its ink.
+ * Groups (separated by 3+ spaces in the OCR text) are slid left-to-right
+ * across the dark-pixel projection until each group locks onto its ink.
+ * Each group becomes one WordPosition — no words are dropped.
  *
- * Font size: fontRatio = 1.0 for all tokens.  The renderer computes the
- * actual font size as medianCellHeightPx * fontRatio * fontScale, which
- * matches the fallback rendering exactly.  The user controls size via the
- * font-scale slider.
+ * The key difference from the cluster algorithm: instead of matching groups
+ * to detected clusters (which can fail when cluster count != group count),
+ * we slide each group sequentially and let it find its own ink.
  *
- * Position: each token's x-position is found by sliding a cursor from left
- * to right and looking for dark-pixel coverage.  Token width (wPct) is
- * computed from canvas measureText proportional to the median cell height,
- * giving visually correct character widths.
- *
- * Guarantees: no words dropped, no complex matching rules needed.
+ * Font size: fontRatio = 1.0 for all (same as fallback rendering).
+ * Width: each group's wPct is measured from canvas measureText, scaled to
+ *        match the rendered font size, so text fills its container exactly.
  */
 export function useSlideWordPositions(
   imageUrl: string,
@@ -58,7 +55,11 @@ export function useSlideWordPositions(
         ctx.drawImage(img, 0, 0)
       }
 
-      // --- Compute median cell height in image pixels ---
+      const refFontSize = 40
+      const fontFam = "'Liberation Sans', Arial, sans-serif"
+      ctx.font = `${refFontSize}px ${fontFam}`
+
+      // --- Median cell height for consistent font sizing ---
       const cellHeights = cells
         .filter(c => c.bbox_pct && c.bbox_pct.h > 0)
         .map(c => Math.round(c.bbox_pct.h / 100 * imgH))
@@ -67,30 +68,9 @@ export function useSlideWordPositions(
         ? cellHeights[Math.floor(cellHeights.length / 2)]
         : 30
 
-      // The renderer computes: fontSize = medianCellHeightPx * fontRatio * fontScale
-      // With fontRatio=1.0 and fontScale=0.7 (default), that's 70% of median cell height.
-      // We need to know how wide each token is at THAT rendered font size,
-      // expressed in image pixels.
-      //
-      // The rendered container is reconWidth px wide = imgW image pixels.
-      // So 1 image pixel = reconWidth/imgW display pixels.
-      // Rendered font size (display px) = medianCellHeightPx_display * 1.0 * fontScale
-      // medianCellHeightPx_display = medianCh * (reconWidth / imgW)
-      // So rendered font = medianCh * (reconWidth/imgW) * fontScale
-      // In image-pixel units: medianCh * fontScale
-      //
-      // measureText at refFontSize=40 gives pixel widths.
-      // Scale from refFontSize → actual image-pixel font size:
-      const refFontSize = 40
-      const fontFam = "'Liberation Sans', Arial, sans-serif"
-      ctx.font = `${refFontSize}px ${fontFam}`
-
-      // Approximate rendered font size in image pixels.
-      // fontScale default is 0.7 but we don't know it here.
-      // Use 0.7 as approximation — the slide positions will still be correct
-      // because we only use this for relative token widths (proportional).
-      const approxFontScale = 0.7
-      const renderedFontImgPx = medianCh * approxFontScale
+      // Scale: measureText (at refFontSize=40) → image pixels at rendered font.
+      // Rendered font in image-pixel units ≈ medianCh * fontScale(0.7).
+      const renderedFontImgPx = medianCh * 0.7
       const measureScale = renderedFontImgPx / refFontSize
 
       const positions = new Map<string, WordPosition[]>()
@@ -98,7 +78,6 @@ export function useSlideWordPositions(
       for (const cell of cells) {
         if (!cell.bbox_pct || !cell.text) continue
 
-        // --- Cell rectangle in image pixels ---
         let cx: number, cy: number
         const cw = Math.round(cell.bbox_pct.w / 100 * imgW)
         const ch = Math.round(cell.bbox_pct.h / 100 * imgH)
@@ -127,71 +106,119 @@ export function useSlideWordPositions(
         }
 
         const threshold = Math.max(1, ch * 0.03)
-
-        // Binary ink mask
         const ink = new Uint8Array(cw)
         for (let x = 0; x < cw; x++) {
           ink[x] = proj[x] >= threshold ? 1 : 0
         }
-
         if (rotation === 180) {
           ink.reverse()
         }
 
-        // --- Tokens ---
-        const tokens = cell.text.split(/\s+/).filter(Boolean)
-        if (tokens.length === 0) continue
+        // --- Split into GROUPS by 3+ spaces (preserving column structure) ---
+        // Then fall back to the full text as a single group.
+        let groups = cell.text.split(/\s{3,}/).map(s => s.trim()).filter(Boolean)
+        if (groups.length === 0) groups = [cell.text.trim()]
+        if (groups.length === 0 || !groups[0]) continue
 
-        // Token widths in image pixels at the approximate rendered font size
-        const tokenWidthsPx = tokens.map(t =>
-          Math.max(4, Math.round(ctx.measureText(t).width * measureScale))
+        // Measure each group's width in image pixels
+        const groupWidthsPx = groups.map(g =>
+          Math.max(4, Math.round(ctx.measureText(g).width * measureScale))
         )
-        const spaceWidthPx = Math.max(2, Math.round(ctx.measureText(' ').width * measureScale))
 
-        // --- Slide each token left-to-right ---
+        // --- Find dark-pixel clusters (contiguous inked regions) ---
+        // Used to determine the ACTUAL ink width for each group (for wPct).
+        const minGap = Math.max(5, Math.round(cw * 0.02))
+        const clusters: { start: number; end: number }[] = []
+        let inCluster = false
+        let clStart = 0
+        let gap = 0
+
+        for (let x = 0; x < cw; x++) {
+          if (ink[x]) {
+            if (!inCluster) { clStart = x; inCluster = true }
+            gap = 0
+          } else if (inCluster) {
+            gap++
+            if (gap > minGap) {
+              clusters.push({ start: clStart, end: x - gap })
+              inCluster = false
+              gap = 0
+            }
+          }
+        }
+        if (inCluster) clusters.push({ start: clStart, end: cw - 1 - gap })
+
+        // Filter narrow clusters (box borders / noise)
+        const minClusterW = Math.max(3, Math.round(cw * 0.005))
+        const filteredClusters = clusters.filter(c => (c.end - c.start + 1) > minClusterW)
+
+        // --- Slide each group left-to-right to find its ink ---
         const wordPos: WordPosition[] = []
         let cursor = 0
 
-        for (let ti = 0; ti < tokens.length; ti++) {
-          const tokenW = tokenWidthsPx[ti]
+        for (let gi = 0; gi < groups.length; gi++) {
+          const groupW = groupWidthsPx[gi]
 
-          // Find first x from cursor where ≥20% of span has ink
-          const coverageNeeded = Math.max(1, Math.round(tokenW * 0.20))
+          // Find the first cluster (from cursor) that has substantial ink
+          // coverage under this group's expected width.
+          const coverageNeeded = Math.max(1, Math.round(groupW * 0.15))
           let bestX = cursor
+          let foundInk = false
 
-          const searchLimit = Math.max(cursor, cw - tokenW)
-
-          for (let x = cursor; x <= searchLimit; x++) {
+          for (let x = cursor; x <= cw - Math.min(groupW, cw); x++) {
             let inkCount = 0
-            const spanEnd = Math.min(x + tokenW, cw)
+            const spanEnd = Math.min(x + groupW, cw)
             for (let dx = 0; dx < spanEnd - x; dx++) {
               inkCount += ink[x + dx]
             }
             if (inkCount >= coverageNeeded) {
               bestX = x
-              break
-            }
-            // Safety: don't scan more than 40% of cell width past cursor
-            if (x > cursor + cw * 0.4 && ti > 0) {
-              bestX = cursor
+              foundInk = true
               break
             }
           }
 
-          // Clamp to cell bounds
-          if (bestX + tokenW > cw) {
-            bestX = Math.max(0, cw - tokenW)
+          // If no ink found, try placing at the matching cluster position
+          if (!foundInk && filteredClusters.length > gi) {
+            bestX = filteredClusters[gi].start
+          } else if (!foundInk) {
+            bestX = cursor
           }
 
+          // Determine width: use the ink span from bestX to the next gap,
+          // but at least the measured text width.
+          let inkEnd = bestX + groupW
+          // Extend to cover the actual ink region starting at bestX
+          for (let x = bestX; x < cw; x++) {
+            if (!ink[x]) {
+              gap = 0
+              for (let gx = x; gx < Math.min(x + minGap + 1, cw); gx++) {
+                if (!ink[gx]) gap++
+                else break
+              }
+              if (gap > minGap) {
+                inkEnd = x
+                break
+              }
+            }
+            inkEnd = x + 1
+          }
+          // Use the larger of: measured text width or actual ink span
+          const actualW = Math.max(groupW, inkEnd - bestX)
+
+          // Clamp
+          const clampedX = Math.min(bestX, cw - 1)
+          const clampedW = Math.min(actualW, cw - clampedX)
+
           wordPos.push({
-            xPct: cell.bbox_pct.x + (bestX / cw) * cell.bbox_pct.w,
-            wPct: (tokenW / cw) * cell.bbox_pct.w,
-            text: tokens[ti],
+            xPct: cell.bbox_pct.x + (clampedX / cw) * cell.bbox_pct.w,
+            wPct: (clampedW / cw) * cell.bbox_pct.w,
+            text: groups[gi],
             fontRatio: 1.0,
           })
 
-          // Advance cursor: past this token + space
-          cursor = bestX + tokenW + spaceWidthPx
+          // Advance cursor past this group's ink region + gap
+          cursor = clampedX + clampedW + minGap
         }
 
         if (wordPos.length > 0) {