why func(make_coco_transforms) do not contains Resize?

[jinsujeon]

As you know, resolution should be aligned.

First, I set Image size to 640 x 640.
But each Images has different size like 1800x1200, 2400x1600

I think If make_coco_transforms revised using Resize Function,
I do not need to change Image resize but function do that.

so, why make_coco_transforms function do not contains resize function.
is there any special reason?

thank you

[JESUSROYETH]

The reason make_coco_transforms doesn’t enforce a fixed image resizing operation by default is to provide flexibility for different training strategies — especially for data augmentation techniques like multi-scale training.

That said, resizing is happening — it just depends on the configuration:

• When multi_scale=True, the function uses a list of different image sizes (computed via compute_multi_scale_scales) and randomly selects one for each image during training. This helps the model generalize better to objects at different scales and improves robustness.
• When multi_scale=False, the scales list contains only a single value — the one you pass in as resolution (e.g., 640) — so all images will be resized to that fixed size.

If you look at make_coco_transforms in rfdetr/datasets/coco.py you’ll see the actual resizing is handled through T.RandomResize and T.RandomSizeCrop, which are wrapped in T.RandomSelect. This setup allows the pipeline to simulate various realistic augmentations during training while still normalizing images in a controlled way.

There's also an alternative pipeline, make_coco_transforms_square_div_64, which applies square resizing (using SquareResize) — handy when working with models that expect square inputs.

Why not just force a fixed size?

Because hard-resizing every image to, say, 640x640 could distort aspect ratios and degrade model performance — especially in object detection. These transformations are designed to resize more intelligently, preserving important spatial features while still normalizing input dimensions when needed.

So...resizing is there, but it’s configurable by design. If you want to always resize to 640x640, just set multi_scale=False and choose the resolution accordingly. You can also tweak square_resize_div_64 depending on whether you want aspect-ratio-preserving or square resizing.

Happy coding!

[jinsujeon]

Thank you for your kindness!

Happy Coding Too

[isaacrob-roboflow]

marking this as resolved