OpenCV and NDI SDK

C++
2

your input Mat is already a decoded image, not a png

remove the pngImage (that isnt one, either !) and the decodePNG call,
and work on your input Mat “as is”

however, since you assume rgba32 data, you should check

m.type() == CV_8UC4

and if it is not so, apply a

cvtConvert(m, m, COLOR_BGR2RGBA);