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+# Feature 7 Plan: PDF Stamp Operation
+
+## Overview
+**Priority:** Phase 2, Priority 6  
+**Endpoint:** `POST /api/pdf/operations/stamp`  
+**Purpose:** Add text/image stamps to PDF documents (watermarks, confidential marks, approval stamps)
+
+---
+
+## Requirements (from CONTROLLER_ENDPOINTS.md)
+
+### Endpoint Specification
+- **Route:** `/api/pdf/operations/stamp`
+- **Method:** POST
+- **Input formats:** 
+  - Multipart/form-data (PDF file + stamp parameters)
+  - JSON (Base64-encoded PDF + stamp parameters)
+- **Output:** Stamped PDF file (application/pdf)
+
+### Stamp Types
+1. **Text Stamp:** Custom text with font, size, color, rotation
+2. **Image Stamp:** PNG/JPEG image overlay
+3. **Predefined Stamps:** "CONFIDENTIAL", "APPROVED", "DRAFT", "VOID" (optional)
+
+### Stamp Parameters
+- **Position:** X, Y coordinates (with Origin support: BottomLeft/TopLeft)
+- **Size:** Width, Height (optional if using image natural size)
+- **Rotation:** Angle in degrees (0-360)
+- **Opacity:** 0.0 (transparent) to 1.0 (opaque)
+- **Page range:** Single page, multiple pages, or "all pages"
+
+---
+
+## Implementation Plan (7 Systematic Commits)
+
+### Commit 1: Domain Layer
+**File:** `DocumentOperator.Domain/Models/ValueObjects/StampType.cs`
+```csharp
+public enum StampType
+{
+    Text,
+    Image,
+    Predefined
+}
+```
+
+**File:** `DocumentOperator.Domain/Models/ValueObjects/PredefinedStampType.cs`
+```csharp
+public enum PredefinedStampType
+{
+    Confidential,
+    Approved,
+    Draft,
+    Void,
+    ForReview
+}
+```
+
+**File:** `DocumentOperator.Domain/Models/ValueObjects/StampPlacement.cs`
+```csharp
+public enum StampPlacement
+{
+    Foreground, // On top of content
+    Background  // Behind content
+}
+```
+
+---
+
+### Commit 2: Infrastructure Interface
+**File:** `DocumentOperator.Application/Common/Interfaces/IPdfProcessor.cs`
+
+Add method:
+```csharp
+/// <summary>
+/// Adds a stamp (text or image) to specified pages of a PDF document.
+/// </summary>
+Task<byte[]> AddStampAsync(
+    Stream pdfStream,
+    StampType stampType,
+    int[]? pageNumbers, // null = all pages
+    (double X, double Y) position,
+    (double Width, double Height)? size = null, // null = auto-size for image
+    AnnotationOrigin origin = AnnotationOrigin.BottomLeft,
+    string? text = null, // Required for Text stamp
+    string? fontName = null, // Default: Arial
+    double? fontSize = null, // Default: 12
+    string? color = null, // Hex color, default: "000000" (black)
+    double? opacity = null, // 0.0-1.0, default: 0.5
+    double? rotation = null, // Degrees, default: 0
+    StampPlacement placement = StampPlacement.Foreground,
+    byte[]? imageBytes = null, // Required for Image stamp
+    PredefinedStampType? predefinedType = null); // Required for Predefined stamp
+```
+
+**Validation rules:**
+- `text` required if `stampType == Text`
+- `imageBytes` required if `stampType == Image`
+- `predefinedType` required if `stampType == Predefined`
+- `pageNumbers` can be null (all pages), empty array not allowed
+- `opacity` must be 0.0-1.0
+- `rotation` must be 0-360
+
+---
+
+### Commit 3: Infrastructure Implementation
+**File:** `DocumentOperator.Infrastructure/Services/PdfProcessing/DevExpressPdfProcessor.cs`
+
+**DevExpress API:**
+- Use `PdfGraphics` to draw on page
+- `PdfGraphics.DrawString()` for text stamps
+- `PdfGraphics.DrawImage()` for image stamps
+- Set opacity via `PdfBrush.Color` alpha channel
+- Apply rotation via `PdfGraphics.RotateTransform()`
+
+**Implementation strategy:**
+1. Load PDF
+2. Validate page numbers against document page count
+3. For each target page:
+   - Get `PdfGraphics` from `PdfDocumentProcessor.CreateGraphics()`
+   - Convert coordinates if `origin == TopLeft`
+   - Apply rotation transform
+   - Set opacity via brush alpha
+   - Draw text/image
+   - Dispose graphics
+4. Save to byte array
+
+**Private helper methods:**
+- `AddTextStamp(PdfGraphics graphics, ...)`
+- `AddImageStamp(PdfGraphics graphics, byte[] imageBytes, ...)`
+- `AddPredefinedStamp(PdfGraphics graphics, PredefinedStampType type, ...)` (delegates to AddTextStamp with predefined text/style)
+- `CalculatePageNumbers(int totalPages, int[]? requestedPages)` → returns array of zero-based indices
+
+---
+
+### Commit 4: Infrastructure Unit Tests
+**File:** `DocumentOperator.Tests/Unit/Infrastructure/Services/PdfProcessing/DevExpressPdfProcessorTests.cs`
+
+**Tests (10-12):**
+1. `AddStampAsync_TextStampSinglePage_ReturnsStampedPdf`
+2. `AddStampAsync_TextStampAllPages_ReturnsStampedPdf`
+3. `AddStampAsync_ImageStampWithRotation_ReturnsStampedPdf`
+4. `AddStampAsync_PredefinedStampConfidential_ReturnsStampedPdf`
+5. `AddStampAsync_WithOpacity_ReturnsStampedPdf`
+6. `AddStampAsync_TopLeftOrigin_ReturnsStampedPdf`
+7. `AddStampAsync_EmptyStream_ThrowsBadRequestException`
+8. `AddStampAsync_InvalidPageNumber_ThrowsBadRequestException`
+9. `AddStampAsync_TextStampWithoutText_ThrowsBadRequestException`
+10. `AddStampAsync_ImageStampWithoutBytes_ThrowsBadRequestException`
+11. `AddStampAsync_InvalidOpacity_ThrowsBadRequestException`
+12. `AddStampAsync_InvalidRotation_ThrowsBadRequestException`
+
+---
+
+### Commit 5: Application Layer
+**File:** `DocumentOperator.Application/AddStamp/AddStampCommand.cs`
+
+**Command/Handler/Validator merged:**
+```csharp
+public record AddStampCommand : IRequest<byte[]>
+{
+    public required Stream PdfStream { get; init; }
+    public required StampType StampType { get; init; }
+    public int[]? PageNumbers { get; init; } // null = all pages
+    public required (double X, double Y) Position { get; init; }
+    public (double Width, double Height)? Size { get; init; }
+    public AnnotationOrigin Origin { get; init; } = AnnotationOrigin.BottomLeft;
+    public string? Text { get; init; }
+    public string? FontName { get; init; }
+    public double? FontSize { get; init; }
+    public string? Color { get; init; }
+    public double? Opacity { get; init; }
+    public double? Rotation { get; init; }
+    public StampPlacement Placement { get; init; } = StampPlacement.Foreground;
+    public byte[]? ImageBytes { get; init; }
+    public PredefinedStampType? PredefinedType { get; init; }
+}
+```
+
+**Validator:**
+- Stream not null
+- Text required if StampType == Text
+- ImageBytes required if StampType == Image
+- PredefinedType required if StampType == Predefined
+- Color regex: `^[0-9A-Fa-f]{6}$`
+- Opacity: 0.0-1.0
+- Rotation: 0-360
+- FontSize > 0 if provided
+
+---
+
+### Commit 6: API Endpoints + DTOs
+**File:** `DocumentOperator.API/Controllers/PdfOperationsController.cs`
+
+**Two endpoints:**
+1. **Multipart:** `POST /api/pdf/operations/stamp` (multipart/form-data)
+2. **JSON:** `POST /api/pdf/operations/stamp` (application/json)
+
+**DTOs:**
+```csharp
+public class AddStampMultipartRequest
+{
+    public required IFormFile File { get; set; }
+    public required StampType StampType { get; set; }
+    public int[]? PageNumbers { get; set; } // Comma-separated in form: "1,3,5"
+    public required double X { get; set; }
+    public required double Y { get; set; }
+    public double? Width { get; set; }
+    public double? Height { get; set; }
+    public AnnotationOrigin Origin { get; set; } = AnnotationOrigin.BottomLeft;
+    public string? Text { get; set; }
+    public string? FontName { get; set; }
+    public double? FontSize { get; set; }
+    public string? Color { get; set; }
+    public double? Opacity { get; set; }
+    public double? Rotation { get; set; }
+    public StampPlacement Placement { get; set; } = StampPlacement.Foreground;
+    public IFormFile? ImageFile { get; set; } // Optional image for Image stamp
+    public PredefinedStampType? PredefinedType { get; set; }
+}
+
+public record AddStampBase64Request
+{
+    public required string Base64Pdf { get; init; }
+    public required StampType StampType { get; init; }
+    public int[]? PageNumbers { get; init; }
+    public required double X { get; init; }
+    public required double Y { get; init; }
+    public double? Width { get; init; }
+    public double? Height { get; init; }
+    public AnnotationOrigin Origin { get; init; } = AnnotationOrigin.BottomLeft;
+    public string? Text { get; init; }
+    public string? FontName { get; init; }
+    public double? FontSize { get; init; }
+    public string? Color { get; init; }
+    public double? Opacity { get; init; }
+    public double? Rotation { get; init; }
+    public StampPlacement Placement { get; init; } = StampPlacement.Foreground;
+    public string? Base64Image { get; init; } // Base64-encoded image bytes
+    public PredefinedStampType? PredefinedType { get; init; }
+}
+```
+
+**Endpoint names:**
+- `Name = "AddStampFromFile"`
+- `Name = "AddStampFromBase64"`
+
+---
+
+### Commit 7: Integration Tests + Documentation
+**File:** `DocumentOperator.Tests/Integration/API/PdfOperationsControllerTests.cs`
+
+**Tests (8-10):**
+1. `AddStampFromFile_TextStampSinglePage_ReturnsStampedPdf`
+2. `AddStampFromBase64_TextStampAllPages_ReturnsStampedPdf`
+3. `AddStampFromFile_ImageStamp_ReturnsStampedPdf`
+4. `AddStampFromBase64_PredefinedStamp_ReturnsStampedPdf`
+5. `AddStampFromBase64_WithRotationAndOpacity_ReturnsStampedPdf`
+6. `AddStampFromBase64_InvalidBase64_Returns400`
+7. `AddStampFromBase64_TextStampWithoutText_Returns400`
+8. `AddStampFromBase64_ImageStampWithoutImage_Returns400`
+9. `AddStampFromBase64_InvalidPageNumber_Returns400`
+10. `AddStampFromBase64_InvalidOpacity_Returns400`
+
+**Update AGENTS.md:**
+- Test count: 101 → ~120 passed
+- PdfOperationsController status: 2/3 → 3/3 endpoints (merge + annotate + stamp ALL DONE)
+- Add Feature 7 to test breakdown
+
+---
+
+## DevExpress API References
+
+**Key classes:**
+- `PdfDocumentProcessor.CreateGraphics(int pageIndex)` → `PdfGraphics`
+- `PdfGraphics.DrawString(string text, PdfFont font, PdfBrush brush, RectangleF bounds)`
+- `PdfGraphics.DrawImage(Image image, RectangleF bounds)`
+- `PdfGraphics.RotateTransform(float angle)`
+- `PdfGraphics.SetTransparency(float opacity)` or use `Color.FromArgb(alpha, r, g, b)`
+- `PdfFont.Create(string fontName, float fontSize)`
+- `PdfBrush.Create(Color color)`
+
+**Coordinate system:**
+- Same as annotations: BottomLeft origin by default
+- Need to convert if user specifies TopLeft
+
+**Stamp placement:**
+- Foreground: Draw after page content (`CreateGraphics` with `PdfGraphicsContentStreamType.Foreground`)
+- Background: Draw before page content (`CreateGraphics` with `PdfGraphicsContentStreamType.Background`)
+
+---
+
+## Potential Challenges
+
+1. **Image format support:** DevExpress may require specific image formats (PNG, JPEG). Need to validate.
+2. **Font availability:** Custom fonts may not be available on server. Default to Arial.
+3. **Text wrapping:** If text is too long, may overflow stamp bounds. Truncate or wrap?
+4. **Performance:** Adding stamp to all pages of large PDF (500+ pages) may be slow. Consider async/streaming.
+
+---
+
+## Estimated Effort
+
+- **Complexity:** Medium (similar to annotation, but with graphics drawing)
+- **Time:** 4-6 hours (7 commits)
+- **Test coverage:** ~20 tests (12 unit + 10 integration)
+- **Expected test count after completion:** ~120 passed, 7 skipped
+
+---
+
+## Success Criteria
+
+✅ All 7 commits completed systematically  
+✅ Build: 0 errors, 0 warnings (ignore DevExpress trial warnings)  
+✅ Tests: ~120 passed, 7 skipped, 0 failed  
+✅ Swagger: Both stamp endpoints visible and testable  
+✅ Documentation: AGENTS.md updated with Feature 7 status  
+
+---
+
+**Ready to start when you approve!** 🎉