Hi,
I suspect the following code has different behavior in C++ and Python.

Scalar a = 1.0;

For Python, the Scalar a = 1.0 code will only replace the first 0.0 to 1.0.
Do something like a[0] = 1.0.
For C++, it will do the Scalar a = Scalar(1.0).

Original link: https://forum.opencv.org/t/image2blobparams-c-and-python/13437?u=zihao_mu
My code in python :

paramTF2cedn = cv.dnn.Image2BlobParams()
paramTF2cedn.datalayout = cv.dnn.DNN_LAYOUT_NHWC;
paramTF2cedn.ddepth = cv.CV_32F;
paramTF2cedn.mean = (128, 128, 128)
paramTF2cedn.scalefactor = 1 / 128.
paramTF2cedn.size = (224, 224)
paramTF2cedn.swapRB = False;
paramTF2cedn.paddingmode = cv.dnn.DNN_PMODE_NULL
print("paramTF2cedn.scalefactor = ", paramTF2cedn.scalefactor)

result is
paramTF2cedn.scalefactor = (0.0078125, 1.0, 1.0, 1.0)

in C++

Image2BlobParams paramTF2cedn;
paramTF2cedn.datalayout = DNN_LAYOUT_NHWC;
paramTF2cedn.ddepth = CV_32F;
paramTF2cedn.mean = (128, 128, 128);
paramTF2cedn.scalefactor = 1 / 128.;
paramTF2cedn.size = Size(224, 224);
paramTF2cedn.swapRB = false;
paramTF2cedn.paddingmode = DNN_PMODE_NULL;
cout << "paramTF2cedn.scalefactor = " << paramTF2cedn.scalefactor << endl;

result is
paramTF2cedn.scalefactor = [0.0078125, 0, 0, 0]

Detailed description

It is about opencv-python bing.

Steps to reproduce

install lastest opencv-python

pip install opencv-python-rolling==4.7.0.20230603.

param = cv.dnn.Image2BlobParams()
param.mean = np.array([0.2, 0.3, 0.4]) # [0.2, 0.3, 0.4, 0.0]
# then redefine it.
param.mean = 1.0 # it is [1.0, 0.3, 0.4, 0.0]  <<--

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues, forum.opencv.org, Stack Overflow, etc and have not found any solution
• I updated to the latest OpenCV version and the issue is still there
• There is reproducer code and related data files (videos, images, onnx, etc)