add-watermark

Instructions

Implementation Reference

• src/index.ts:475-510 (handler)

  The handler function that adds a watermark to an image using ImageMagick. It resolves absolute paths, normalizes opacity, constructs and executes the composite command with specified gravity position, and handles output path generation.

  async ({ inputPath, watermarkPath, position, opacity, outputPath, outputFilename }) => {
    try {
      await checkImageMagick();
      const absoluteInputPath = await getAbsolutePath(inputPath);
      const absoluteWatermarkPath = await getAbsolutePath(watermarkPath);
      const inputFileName = absoluteInputPath.split('/').pop()?.split('.')[0] || 'output';
      const extension = absoluteInputPath.split('.').pop() || 'png';
      const defaultFilename = outputFilename || `${inputFileName}_watermarked.${extension}`;
      const finalOutputPath = await getOutputPath(outputPath, defaultFilename);
  
      // Convert opacity from 0-100 to 0-1 for ImageMagick
      const normalizedOpacity = opacity / 100;
  
      const command = `convert "${absoluteInputPath}" \\( "${absoluteWatermarkPath}" -alpha set -channel A -evaluate multiply ${normalizedOpacity} \\) -gravity ${position} -composite "${finalOutputPath}"`;
      await execSync(command);
  
      return {
        content: [
          {
            type: "text",
            text: `Watermark successfully added and saved to: ${finalOutputPath}`,
          },
        ],
      };
    } catch (error) {
      const errorMessage = error instanceof Error ? error.message : String(error);
      return {
        content: [
          {
            type: "text",
            text: `Error adding watermark: ${errorMessage}`,
          },
        ],
      };
    }
  }

• src/index.ts:467-474 (schema)

  Zod input schema for the add-watermark tool defining parameters like inputPath, watermarkPath, position (ImageMagick gravity enum), opacity, and optional output paths.

  {
    inputPath: z.string().describe("Absolute path to input image file"),
    watermarkPath: z.string().describe("Absolute path to watermark image file"),
    position: z.enum(['northwest', 'north', 'northeast', 'west', 'center', 'east', 'southwest', 'south', 'southeast']).default('southeast').describe("Position of watermark"),
    opacity: z.number().min(0).max(100).default(50).describe("Watermark opacity (0-100)"),
    outputPath: z.string().optional().describe("Optional absolute path for output file. If not provided, file will be saved in Downloads folder"),
    outputFilename: z.string().optional().describe("Output filename (only used if outputPath is not provided)")
  },

• src/index.ts:464-511 (registration)

  The server.tool registration call for the add-watermark tool, including name, description, input schema, and inline handler function.

  server.tool(
    "add-watermark",
    "Add watermark to image",
    {
      inputPath: z.string().describe("Absolute path to input image file"),
      watermarkPath: z.string().describe("Absolute path to watermark image file"),
      position: z.enum(['northwest', 'north', 'northeast', 'west', 'center', 'east', 'southwest', 'south', 'southeast']).default('southeast').describe("Position of watermark"),
      opacity: z.number().min(0).max(100).default(50).describe("Watermark opacity (0-100)"),
      outputPath: z.string().optional().describe("Optional absolute path for output file. If not provided, file will be saved in Downloads folder"),
      outputFilename: z.string().optional().describe("Output filename (only used if outputPath is not provided)")
    },
    async ({ inputPath, watermarkPath, position, opacity, outputPath, outputFilename }) => {
      try {
        await checkImageMagick();
        const absoluteInputPath = await getAbsolutePath(inputPath);
        const absoluteWatermarkPath = await getAbsolutePath(watermarkPath);
        const inputFileName = absoluteInputPath.split('/').pop()?.split('.')[0] || 'output';
        const extension = absoluteInputPath.split('.').pop() || 'png';
        const defaultFilename = outputFilename || `${inputFileName}_watermarked.${extension}`;
        const finalOutputPath = await getOutputPath(outputPath, defaultFilename);
  
        // Convert opacity from 0-100 to 0-1 for ImageMagick
        const normalizedOpacity = opacity / 100;
  
        const command = `convert "${absoluteInputPath}" \\( "${absoluteWatermarkPath}" -alpha set -channel A -evaluate multiply ${normalizedOpacity} \\) -gravity ${position} -composite "${finalOutputPath}"`;
        await execSync(command);
  
        return {
          content: [
            {
              type: "text",
              text: `Watermark successfully added and saved to: ${finalOutputPath}`,
            },
          ],
        };
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return {
          content: [
            {
              type: "text",
              text: `Error adding watermark: ${errorMessage}`,
            },
          ],
        };
      }
    }
  );

• src/index.ts:30-44 (helper)

  Helper function to resolve input paths to absolute paths, checking existence; used for both input and watermark paths.

  async function getAbsolutePath(inputPath: string): Promise<string> {
    if (isAbsolute(inputPath)) {
      return inputPath;
    }
    
    // FIXME: But it's not working, because the server is running in a different directory
    const absolutePath = resolve(process.cwd(), inputPath);
    
    try {
      await fs.access(absolutePath);
      return absolutePath;
    } catch (error) {
      throw new Error(`Input file not found: ${inputPath}`);
    }
  }

• src/index.ts:69-76 (helper)

  Helper function to verify ImageMagick installation by running 'convert -version'; called at start of handler.

  async function checkImageMagick() {
    try {
      execSync('convert -version');
      return true;
    } catch (error) {
      throw new Error('ImageMagick is not installed. Please install it first.');
    }
  }