dnn openpose sample - expected image resolution

asked 2018-05-17 02:01:38 -0600

visez
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updated 2018-05-17 03:59:08 -0600

In the dnn/openpose.cpp using the network definition from CMU at prototxt link the input layer shape is given as [1,3,368,368].

Does it mean that the network is expecting a square image as an input? What happens if an image is given in its original aspect ratio?

The current implementation of the openpose library defines the input layer shape at runtime: prototxt link, is it possible to do something similar with opencv?

answered 2018-05-17 04:03:46 -0600

berak
32993 ●7 ●81 ●312

updated 2018-05-17 04:04:25 -0600

Does it mean that the network is expecting a square image as an input?

it means it will resize the input image to 368x368 (the network was trained on this) , you don't need to do this, it is done in blobFromImage()

changing the width or height values might not be a good idea (for this pretrained model), as the resulting heatmap shapes will change, and the overall accuracy will go down.

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Thank you. From the blobFromImage() definition and leaving the default parameters, it looks like the image will be first resized uniformly so that the smallest dimension is equal to 368, and then cropped from the center.

For a standard widescreen 1280x720 image, that means that the left and right sides of the image will be cropped away, so no person should be detected if it's outside the central region, is that correct?

visez ( 2018-05-17 04:15:35 -0600 )edit

yes, you're right about the cropping.

maybe using inages that large is a bad idea in the 1st place here, since the heatmaps are only 46x46. so, the larger the image, the larger the position error

berak ( 2018-05-17 04:22:11 -0600 )edit

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