merge_images

Instructions

Implementation Reference

• index.js:237-317 (handler)

  The handler function that performs the logic of merging multiple images based on input parameters (layout, gap, etc.) using the sharp library.

    async ({ input_paths, layout = "horizontal", gap = 0, background = "#ffffff", output_path }) => {
      try {
        // Load metadata for all images
        const metas = await Promise.all(input_paths.map(async (p) => {
          await fs.access(p);
          const meta = await sharp(p).metadata();
          return { path: p, width: meta.width, height: meta.height };
        }));
  
        // Parse background color
        let bg = { r: 255, g: 255, b: 255, alpha: 1 };
        const hex = background.replace('#', '');
        if (hex.length === 6) {
          bg = { r: parseInt(hex.slice(0,2),16), g: parseInt(hex.slice(2,4),16), b: parseInt(hex.slice(4,6),16), alpha: 1 };
        }
  
        let canvasW, canvasH, positions;
  
        if (layout === "horizontal") {
          canvasH = Math.max(...metas.map(m => m.height));
          canvasW = metas.reduce((sum, m) => sum + m.width, 0) + gap * (metas.length - 1);
          positions = [];
          let x = 0;
          for (const m of metas) {
            positions.push({ x, y: Math.floor((canvasH - m.height) / 2) });
            x += m.width + gap;
          }
        } else if (layout === "vertical") {
          canvasW = Math.max(...metas.map(m => m.width));
          canvasH = metas.reduce((sum, m) => sum + m.height, 0) + gap * (metas.length - 1);
          positions = [];
          let y = 0;
          for (const m of metas) {
            positions.push({ x: Math.floor((canvasW - m.width) / 2), y });
            y += m.height + gap;
          }
        } else {
          // grid: auto columns = ceil(sqrt(n))
          const cols = Math.ceil(Math.sqrt(metas.length));
          const rows = Math.ceil(metas.length / cols);
          const cellW = Math.max(...metas.map(m => m.width));
          const cellH = Math.max(...metas.map(m => m.height));
          canvasW = cols * cellW + gap * (cols - 1);
          canvasH = rows * cellH + gap * (rows - 1);
          positions = metas.map((m, i) => {
            const col = i % cols;
            const row = Math.floor(i / cols);
            return {
              x: col * (cellW + gap) + Math.floor((cellW - m.width) / 2),
              y: row * (cellH + gap) + Math.floor((cellH - m.height) / 2),
            };
          });
        }
  
        // Build composite layers
        const composites = await Promise.all(metas.map(async (m, i) => ({
          input: await sharp(m.path).toBuffer(),
          left: positions[i].x,
          top: positions[i].y,
        })));
  
        const outExt = path.extname(output_path).slice(1).toLowerCase() || "png";
        const formatMap = { jpg: "jpeg" };
        const fmt = formatMap[outExt] || outExt;
  
        await sharp({
          create: { width: canvasW, height: canvasH, channels: 4, background: bg },
        })
          .composite(composites)
          .toFormat(fmt)
          .toFile(output_path);
  
        const stat = await fs.stat(output_path);
        return {
          content: [{ type: "text", text: JSON.stringify({ success: true, output_path, width: canvasW, height: canvasH, size_bytes: stat.size }) }],
        };
      } catch (err) {
        return { isError: true, content: [{ type: "text", text: `Error: ${err.message}` }] };
      }
    }
  );

• index.js:227-236 (registration)

  Registration of the "merge_images" tool with schema definitions for input arguments using Zod.

  server.tool(
    "merge_images",
    "Merge multiple images into a single image by arranging them horizontally, vertically, or in a grid.",
    {
      input_paths: z.array(z.string()).min(2).describe("Ordered list of absolute paths to the images to merge (minimum 2)"),
      layout: z.enum(["horizontal", "vertical", "grid"]).optional().default("horizontal").describe("Arrangement: horizontal (side by side), vertical (stacked), or grid (auto columns)"),
      gap: z.number().int().min(0).optional().default(0).describe("Gap in pixels between images (default 0)"),
      background: z.string().optional().default("#ffffff").describe("Background/gap fill color as hex (default #ffffff)"),
      output_path: z.string().describe("Absolute path for the output file (format inferred from extension)"),
    },