> For the complete documentation index, see [llms.txt](https://docs.augelab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.augelab.com/function-blocks/blocks-reference/image-transformations/operations/image-concatenate.md).

# Image Concatenate

This function block merges multiple images into a single image by placing them side-by-side (horizontal) or one after another (vertical). It automatically aligns images by adding borders when input images have different dimensions so you get a clean, single output image.

## 📥 Inputs <a href="#inputs" id="inputs"></a>

* `Image List` Input socket that accepts one or more images to be concatenated (multiple images supported).

## 📤 Outputs <a href="#outputs" id="outputs"></a>

* `Image` Output socket that provides the concatenated image.

## 🕹️ Controls <a href="#controls" id="controls"></a>

* `Relation` Dropdown to choose the concatenation direction.
  * Choose between HORIZONTAL or VERTICAL arrangement.

## 🎯 Key Features <a href="#features" id="features"></a>

* Automatic alignment: when input images differ in width or height, the block adds borders to match sizes so images align correctly.
* Supports multiple inputs: feed a list of images and the block will produce a single combined image.
* Simple orientation switch: toggle between horizontal and vertical concatenation with the `Relation` control.

## ⚙️ Running mechanism <a href="#running-mechanism" id="running-mechanism"></a>

When executed, the block reads the provided image list, ensures each image has matching dimensions by adding borders if needed, and then merges them according to the chosen `Relation`. The resulting image is sent to the `Image` output socket for downstream blocks or display.

## 📝 Usage <a href="#usage" id="usage"></a>

1. Provide images to the `Image List` input — you can connect multiple image-producing blocks or a list of images.
2. Select the desired layout with the `Relation` dropdown.
3. Read the combined result from the `Image` output and use it for display, logging, or further processing.

## 💡 Tips and Tricks <a href="#tips-and-tricks" id="tips-and-tricks"></a>

* If you want consistent results without visible borders, use `Image Resizer` or `Image Resize` before this block to make all images the same size.
* To control padding color or add custom margins, prepare images with `Image Padding` first, then concatenate.
* Crop inputs to the exact regions you want to combine using `Image ROI Select` or `Image ROI` before feeding them here.
* Use `Show Image` to preview the concatenated result interactively.
* For saving or recording the combined output, connect the `Image` output to `Image Logger` or `Image Write`.
* If you want a collage-style layout with borders indicating OK/NOK states, consider `Collage Images` as an alternative or follow-up block.

## 🛠️ Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* Unexpected black borders: images have different aspect ratios. Either accept the borders, or use `Image Resizer` / `Image Padding` / `Image ROI Select` to make input sizes match.
* Empty or missing output: ensure every input in the `Image List` is a valid image. Use an image preview block like `Show Image` upstream to verify inputs.
* Very tall or wide output: choose VERTICAL or HORIZONTAL `Relation` appropriately or resize inputs to a manageable dimension before concatenation.