Fix image stamp cropping and align preview with PDF output for add-stamp (#6013)

app/core/src/main/java/stirling/software/SPDF/controller/api/misc/StampController.java

@@ -483,9 +483,19 @@ public class StampController {
             y = overrideY;
         } else {
             x = calculatePositionX(pageSize, position, desiredPhysicalWidth, margin);
-            y = calculatePositionY(pageSize, position, desiredPhysicalHeight, margin);
+            // drawImage() places the lower-left corner at (x, y); use image-specific Y logic
+            y = calculateImagePositionY(pageSize, position, desiredPhysicalHeight, margin);
         }
 
+        float llx = pageSize.getLowerLeftX();
+        float lly = pageSize.getLowerLeftY();
+        float urx = pageSize.getUpperRightX();
+        float ury = pageSize.getUpperRightY();
+        float xMax = Math.max(llx, urx - desiredPhysicalWidth);
+        float yMax = Math.max(lly, ury - desiredPhysicalHeight);
+        x = Math.min(xMax, Math.max(llx, x));
+        y = Math.min(yMax, Math.max(lly, y));
+
         contentStream.saveGraphicsState();
         contentStream.transform(Matrix.getTranslateInstance(x, y));
         contentStream.transform(Matrix.getRotateInstance(Math.toRadians(rotation), 0, 0));
@@ -495,18 +505,37 @@ public class StampController {
 
     private float calculatePositionX(
             PDRectangle pageSize, int position, float contentWidth, float margin) {
+        float llx = pageSize.getLowerLeftX();
+        float urx = pageSize.getUpperRightX();
         return switch (position % 3) {
             case 1: // Left
-                yield pageSize.getLowerLeftX() + margin;
+                yield llx + margin;
             case 2: // Center
-                yield (pageSize.getWidth() - contentWidth) / 2;
+                yield llx + (pageSize.getWidth() - contentWidth) / 2;
             case 0: // Right
-                yield pageSize.getUpperRightX() - contentWidth - margin;
+                yield urx - contentWidth - margin;
             default:
                 yield 0;
         };
     }
 
+    private float calculateImagePositionY(
+            PDRectangle pageSize, int position, float imageHeight, float margin) {
+        float lly = pageSize.getLowerLeftY();
+        float pageHeight = pageSize.getHeight();
+        float ury = pageSize.getUpperRightY();
+        return switch ((position - 1) / 3) {
+            case 0: // Top - upper image edge flush below top margin
+                yield ury - margin - imageHeight;
+            case 1: // Middle - center image on page
+                yield lly + (pageHeight - imageHeight) / 2;
+            case 2: // Bottom - lower image edge at bottom margin
+                yield lly + margin;
+            default:
+                yield lly;
+        };
+    }
+
     private float calculatePositionY(
             PDRectangle pageSize, int position, float height, float margin) {
         return switch ((position - 1) / 3) {

app/core/src/test/java/stirling/software/SPDF/controller/api/misc/StampControllerTest.java

@@ -9,6 +9,7 @@ import java.util.regex.Pattern;
 
 import org.apache.pdfbox.pdmodel.PDDocument;
 import org.apache.pdfbox.pdmodel.PDDocumentInformation;
+import org.apache.pdfbox.pdmodel.common.PDRectangle;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
@@ -46,6 +47,7 @@ class StampControllerTest {
 
     private Method processStampTextMethod;
     private Method processCustomDateFormatMethod;
+    private Method calculateImagePositionYMethod;
 
     @BeforeEach
     void setUp() throws NoSuchMethodException {
@@ -63,6 +65,26 @@ class StampControllerTest {
                 StampController.class.getDeclaredMethod(
                         "processCustomDateFormat", String.class, LocalDateTime.class);
         processCustomDateFormatMethod.setAccessible(true);
+
+        calculateImagePositionYMethod =
+                StampController.class.getDeclaredMethod(
+                        "calculateImagePositionY",
+                        PDRectangle.class,
+                        int.class,
+                        float.class,
+                        float.class);
+        calculateImagePositionYMethod.setAccessible(true);
+    }
+
+    private float invokeCalculateImagePositionY(
+            PDRectangle pageSize, int position, float imageHeight, float margin) throws Exception {
+        try {
+            return (float)
+                    calculateImagePositionYMethod.invoke(
+                            stampController, pageSize, position, imageHeight, margin);
+        } catch (InvocationTargetException e) {
+            throw (Exception) e.getCause();
+        }
     }
 
     private String invokeProcessStampText(
@@ -86,6 +108,45 @@ class StampControllerTest {
         }
     }
 
+    @Nested
+    @DisplayName("Image stamp position (lower-left anchor)")
+    class ImagePositionYTests {
+
+        @Test
+        @DisplayName("Top row: upper edge of image sits below top margin")
+        void topRowUsesUpperRightMinusMarginMinusHeight() throws Exception {
+            PDRectangle page = new PDRectangle(0, 0, 600, 800);
+            float y = invokeCalculateImagePositionY(page, 3, 100f, 10f);
+            assertEquals(690f, y, 0.001f);
+        }
+
+        @Test
+        @DisplayName("Middle row: image is vertically centred on page")
+        void middleRowCentresImage() throws Exception {
+            PDRectangle page = new PDRectangle(0, 0, 600, 800);
+            float y = invokeCalculateImagePositionY(page, 5, 100f, 10f);
+            assertEquals(350f, y, 0.001f);
+        }
+
+        @Test
+        @DisplayName("Bottom row: lower edge of image sits above bottom margin")
+        void bottomRowUsesLowerLeftPlusMargin() throws Exception {
+            PDRectangle page = new PDRectangle(0, 0, 600, 800);
+            float y = invokeCalculateImagePositionY(page, 7, 100f, 10f);
+            assertEquals(10f, y, 0.001f);
+        }
+
+        @Test
+        @DisplayName("Honours non-zero media box origin")
+        void respectsLowerLeftOrigin() throws Exception {
+            PDRectangle page = new PDRectangle(50f, 100f, 400f, 300f);
+            float yMid = invokeCalculateImagePositionY(page, 5, 20f, 5f);
+            assertEquals(240f, yMid, 0.001f);
+            float yTop = invokeCalculateImagePositionY(page, 3, 20f, 5f);
+            assertEquals(375f, yTop, 0.001f);
+        }
+    }
+
     @Nested
     @DisplayName("Basic Variable Substitution Tests")
     class BasicVariableTests {

frontend/src/core/components/tools/addStamp/StampPreview.tsx

@@ -63,7 +63,8 @@ export default function StampPreview({ parameters, onParameterChange, file, show
         const buffer = await file.arrayBuffer();
         const pdf = await pdfWorkerManager.createDocument(buffer, { disableAutoFetch: true, disableStream: true });
         const page = await pdf.getPage(1);
-        const viewport = page.getViewport({ scale: 1 });
+        // Unrotated viewport keeps points to pixels aligned and avoids width and height swaps
+        const viewport = page.getViewport({ scale: 1, rotation: 0 });
         if (!cancelled) {
           setPageSize({ widthPts: viewport.width, heightPts: viewport.height });
         }
@@ -143,8 +144,10 @@ export default function StampPreview({ parameters, onParameterChange, file, show
       const heightPts = pageSize?.heightPts ?? 841.89;
       const scaleX = containerSize.width / widthPts;
       const scaleY = containerSize.height / heightPts;
-      const newLeftPts = Math.max(0, Math.min(containerSize.width, newLeftPx)) / scaleX;
+      const maxLeftPx = Math.max(0, containerSize.width - widthPx);
-      const newBottomPts = Math.max(0, Math.min(containerSize.height, newBottomPx)) / scaleY;
+      const maxBottomPx = Math.max(0, containerSize.height - heightPx);
+      const newLeftPts = Math.max(0, Math.min(maxLeftPx, newLeftPx)) / scaleX;
+      const newBottomPts = Math.max(0, Math.min(maxBottomPx, newBottomPx)) / scaleY;
       onParameterChange('overrideX', newLeftPts as any);
       onParameterChange('overrideY', newBottomPts as any);
     }
@@ -153,7 +156,7 @@ export default function StampPreview({ parameters, onParameterChange, file, show
   }, [parameters.fontSize, style.item, containerSize, pageSize, showQuickGrid, parameters.overrideX, parameters.overrideY, onParameterChange]);
 
   // Drag/resize/rotate interactions
-  const draggingRef = useRef<{ type: 'move' | 'resize' | 'rotate'; startX: number; startY: number; initLeft: number; initBottom: number; initHeight: number; centerX: number; centerY: number } | null>(null);
+  const draggingRef = useRef<{ type: 'move' | 'resize' | 'rotate'; startX: number; startY: number; initLeft: number; initBottom: number; initWidth: number; initHeight: number; centerX: number; centerY: number } | null>(null);
 
   const ensureOverrides = () => {
     const pageWidth = containerSize.width;
@@ -164,13 +167,17 @@ export default function StampPreview({ parameters, onParameterChange, file, show
     const itemStyle = style.item as any;
     const leftPx = parseFloat(String(itemStyle.left).replace('px', '')) || 0;
     const bottomPx = parseFloat(String(itemStyle.bottom).replace('px', '')) || 0;
+    const widthPx = parseFloat(String(itemStyle.width).replace('px', '')) || 0;
+    const heightPx = parseFloat(String(itemStyle.height).replace('px', '')) || 0;
     const widthPts = pageSize?.widthPts ?? 595.28;
     const heightPts = pageSize?.heightPts ?? 841.89;
     const scaleX = containerSize.width / widthPts;
     const scaleY = containerSize.height / heightPts;
     if (parameters.overrideX < 0 || parameters.overrideY < 0) {
-      onParameterChange('overrideX', Math.max(0, Math.min(pageWidth, leftPx)) / scaleX as any);
+      const maxLeftPx = Math.max(0, pageWidth - widthPx);
-      onParameterChange('overrideY', Math.max(0, Math.min(pageHeight, bottomPx)) / scaleY as any);
+      const maxBottomPx = Math.max(0, pageHeight - heightPx);
+      onParameterChange('overrideX', Math.max(0, Math.min(maxLeftPx, leftPx)) / scaleX as any);
+      onParameterChange('overrideY', Math.max(0, Math.min(maxBottomPx, bottomPx)) / scaleY as any);
     }
   };
 
@@ -194,6 +201,7 @@ export default function StampPreview({ parameters, onParameterChange, file, show
       startY: (rect ? rect.bottom - e.clientY : 0), // convert to bottom-based coords
       initLeft: left,
       initBottom: bottom,
+      initWidth: width,
       initHeight: height,
       centerX,
       centerY,
@@ -215,8 +223,10 @@ export default function StampPreview({ parameters, onParameterChange, file, show
     if (drag.type === 'move') {
       const dx = x - drag.startX;
       const dy = y - drag.startY;
-      const newLeftPx = Math.max(0, Math.min(containerSize.width, drag.initLeft + dx));
+      const maxLeftPx = Math.max(0, containerSize.width - drag.initWidth);
-      const newBottomPx = Math.max(0, Math.min(containerSize.height, drag.initBottom + dy));
+      const maxBottomPx = Math.max(0, containerSize.height - drag.initHeight);
+      const newLeftPx = Math.max(0, Math.min(maxLeftPx, drag.initLeft + dx));
+      const newBottomPx = Math.max(0, Math.min(maxBottomPx, drag.initBottom + dy));
       const widthPts = pageSize?.widthPts ?? 595.28;
       const heightPts = pageSize?.heightPts ?? 841.89;
       const scaleX = containerSize.width / widthPts;

frontend/src/core/components/tools/addStamp/StampPreviewUtils.ts

@@ -88,10 +88,12 @@ export function computeStampPreviewStyle(
   const marginPts = (widthPts + heightPts) / 2 * (marginFactorMap[parameters.customMargin] ?? 0.035);
 
   // Compute content dimensions
-  const heightPtsContent = parameters.fontSize * getAlphabetPreviewScale(parameters.alphabet);
+  const heightPtsContent =
+    parameters.stampType === 'image'
+      ? parameters.fontSize
+      : parameters.fontSize * getAlphabetPreviewScale(parameters.alphabet);
   let widthPtsContent = heightPtsContent;
 
-
   if (parameters.stampType === 'image' && imageMeta) {
     const aspect = imageMeta.width / imageMeta.height;
     widthPtsContent = heightPtsContent * aspect;
@@ -222,7 +224,7 @@ export function computeStampPreviewStyle(
       height: `${heightPx}px`,
       opacity: displayOpacity,
       transform: `rotate(${-parameters.rotation}deg)`,
-      transformOrigin: 'center center',
+      transformOrigin: parameters.stampType === 'image' ? 'left bottom' : 'center center',
       color: parameters.customColor,
       display: 'flex',
       flexDirection: 'column',