Transparency (alpha) band of PNG images not used when training

A normal image is composed by red, green, and blue (RGB) channels. Some image format, like .png, allow to have 4, where the 4th usually it's the transparency of the image (this is called alpha channel sometimes). In most of our dataset, we exploit this extra channel to put an extra color information, the infrared band (since we use satellite images with 4 bands). When we upload PNG images with 4 bands, and then we download it back from roboflow, this information is lost, as the downloaded images have in the alpha band only 255 as value, and also the RGB values seems slightly modified.

I'm attaching to this email a link to a COCO dataset that can be uploaded to debug this problem: here

Inizia riproducendo il problema con il dataset COCO collegato e le immagini PNG a quattro bande, confrontando le immagini caricate con i risultati scaricati. Il lavoro è completato quando i PNG scaricati preservano i valori delle bande alpha/infrarossa e non modificano inaspettatamente i canali RGB.