Image Merger
How to Merge Multiple Images Horizontally or Vertically in .NET

How to Merge Multiple Images Horizontally or Vertically in .NET

Merging photos into a single output is essential for banners, product collages, and comparison shots. Aspose.Imaging for .NET makes it easy to combine images horizontally or vertically—at any scale and with any format.

Real-World Problem

Manual photo merging is slow and inconsistent—especially when handling folders of images or creating composite collages for web/e-commerce. Automation ensures fast, repeatable, and pixel-perfect results.

Solution Overview

With Aspose.Imaging for .NET, you can programmatically load, size, and draw any number of images into a single horizontal or vertical canvas. The result is a single composite image ready for web, print, or analysis.

Prerequisites

  1. Visual Studio 2019 or later
  2. .NET 6.0 or later (or .NET Framework 4.6.2+)
  3. Aspose.Imaging for .NET from NuGet
  4. Folder of images to merge (JPG, PNG, BMP, etc.)
PM> Install-Package Aspose.Imaging

Step-by-Step Implementation

Step 1: Organize Images and Choose Merge Direction 

bool mergeHorizontal = true; // set false for vertical
string[] files = Directory.GetFiles("./input", "*.jpg");

Step 2: Load Images and Calculate Output Size 

var images = files.Select(f => Image.Load(f)).ToList();
int totalWidth = mergeHorizontal ? images.Sum(img => img.Width) : images.Max(img => img.Width);
int totalHeight = mergeHorizontal ? images.Max(img => img.Height) : images.Sum(img => img.Height);

Step 3: Create Output Image and Draw Each Source 

using (var outImg = Image.Create(new PngOptions(), totalWidth, totalHeight))
{
    var graphics = new Aspose.Imaging.Graphics(outImg);
    int x = 0, y = 0;
    foreach (var img in images)
    {
        graphics.DrawImage(img, new Aspose.Imaging.Rectangle(x, y, img.Width, img.Height));
        if (mergeHorizontal)
            x += img.Width;
        else
            y += img.Height;
    }
    outImg.Save("./output/merged.png");
}
images.ForEach(img => img.Dispose());

Step 4: Validate Output and Handle Errors

  • Preview result, check for misalignment or format issues.
  • Always dispose images after use to free memory.

Step 5: Handle Mixed Sizes or Formats

  • Add logic to center images or fill with background color if source images vary in size.

Use Cases and Applications

  • E-commerce product or color comparisons
  • Photo collages for marketing and social posts
  • Scanning and archiving page composites
  • Before/after visualizations in web apps

Common Challenges and Solutions

Challenge 1: Images Are Different Sizes

Solution: Pad with a background or align (top/center/bottom) as needed before drawing.

Challenge 2: Output Image Is Too Large

Solution: Limit number of images or resize before merging for web-ready output.

Challenge 3: Memory or Alignment Errors

Solution: Dispose all loaded images, double-check coordinate math, and preview output.

Performance Considerations

  • Use PNG for lossless merges, JPEG for web speed
  • Monitor memory for large merges—dispose all image objects
  • Test with representative images before production runs

Best Practices

  1. Organize images in desired order before merge
  2. Preview output for alignment/overlap issues
  3. Use naming conventions for repeatable batches
  4. Document settings for pipeline reuse

Advanced Scenarios

Scenario 1: Create Grid/Mosaic Layouts

Combine horizontal and vertical logic for 2D photo mosaics.

Scenario 2: Add Labels, Borders, or Effects

Use Graphics to add text or outlines for clarity in collages.

FAQ

Q: Can I merge different file types together? A: Yes, just load each format—output can be any supported type.

Q: How do I merge a folder of hundreds of images? A: Merge in smaller batches or resize images before combining.

Q: Can I automate layout for complex collages? A: Yes, programmatically calculate positions for any pattern or grid.

Conclusion

Aspose.Imaging for .NET enables fast, reliable image merging for any use case—horizontal, vertical, or custom layout—all fully automated.

See Aspose.Imaging for .NET API Reference for advanced merging and composite examples.

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