# Is there any workflow block that can join a number of output images into one?
**URL:** https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032
**Category:** 🤝 Community Help
**Created:** [August 28, 2025, 8:19am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032 "2025-08-28T08:19:49Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Anthony\_Dunk](https://discuss.roboflow.com/u/Anthony_Dunk)
#### Post date: [August 28, 2025, 8:19am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/1 "2025-08-28T08:19:49Z")
I have a workflow which produces 6 output images that I want to join side-by-side into a single output image. Are there any existing Roboflow blocks that could do this, or would I need to try and create a custom block for this purpose? If the later, how hard is it to do for an experienced developer who has only a fairly basic grasp of the Python language? Thanks.
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### Author:  [@brad](https://discuss.roboflow.com/u/brad)
#### Post date: [August 28, 2025, 7:28pm UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/2 "2025-08-28T19:28:02Z")
[Grid Vizualization](https://inference.roboflow.com/workflows/blocks/grid_visualization/) is the closest (but will combine them into an n x n grid vs a straight line). We’d [welcome a PR](https://github.com/roboflow/inference/blob/main/inference/core/workflows/core_steps/visualizations/grid/v1.py) to extend it to be able to stack horizontally or vertically though!
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### Author:  [@Anthony\_Dunk](https://discuss.roboflow.com/u/Anthony_Dunk)
#### Post date: [August 28, 2025, 11:42pm UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/3 "2025-08-28T23:42:36Z")
Thanks. I tried to add that one to my workflow, but it seems that the input to Grid Vizualization block is incompatible with the output of Image Slicer. I don’t understand why since image slicer produces a set of images, and that is what the documentation says Grid Visualization takes as input… Is it a case of a list vs an array or something like that? If so, is there anyway to adapt the Image Slicer output to be compatible with the input of Grid Visualization?
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### Author:  [@brad](https://discuss.roboflow.com/u/brad)
#### Post date: [August 29, 2025, 12:07am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/4 "2025-08-29T00:07:01Z")
Image Slicer produces a Batch of images. It’s stacked in a different dimension (for running operations in parallel). To convert a Batch into a list, use the [Dimension Collapse](https://inference.roboflow.com/workflows/blocks/dimension_collapse/) block. The output of that could be passed to Grid Visualization.
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### Author:  [@Anthony\_Dunk](https://discuss.roboflow.com/u/Anthony_Dunk)
#### Post date: [August 29, 2025, 12:44am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/5 "2025-08-29T00:44:12Z")
Thanks. But whenever I add a Dimension Collapse block in my workflow where the input is an image or a list of images, I get the message “Internal error” with no other details. The only way I could avoid this error was to connect the Dimension Collapse block to the output of the Dynamic Zone block, but this is not what I need it for.
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### Author:  [@Anthony\_Dunk](https://discuss.roboflow.com/u/Anthony_Dunk)
#### Post date: [August 29, 2025, 1:01am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/6 "2025-08-29T01:01:04Z")
Maybe if I explain more what I’m trying to do it will help see if there is a solution within Roboflow. I’m detecting a rectangular box in an image, doing a perspective correction warp to make it rectangular in pixel space, then using Image Slicer to cut it up into 6 horizontal rows, then rotating each row to be a vertical image. This is working fine, but the final step is that I want to combine these 6 rotated vertical images into a single long vertical image. For this I would need a block that does the exact opposite to Image Slicer. At the moment, the only way I can do this is run the workflow from Python and do the final image processing step there.
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### Author:  [@Anthony\_Dunk](https://discuss.roboflow.com/u/Anthony_Dunk)
#### Post date: [September 2, 2025, 6:30am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/7 "2025-09-02T06:30:50Z")
Ok. So I finally worked out how to do this… I created a custom block in Roboflow so I could resize and join the images together using the numpy and cv2 libraries. I found that I had to add a dimension collapse block before my custom block though so that I could iterate through the images output by Image Slicer as a list of values. So that part of your previous advice was helpful.
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### Author:  [@system](https://discuss.roboflow.com/u/system)
#### Post date: [September 9, 2025, 6:31am UTC](https://discuss.roboflow.com/t/is-there-any-workflow-block-that-can-join-a-number-of-output-images-into-one/11032/8 "2025-09-09T06:31:22Z")
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