Artifacts in saved images

[jonashein]

Hi all,

I'm currently trying to apply Zebrapose to my own dataset. I've sucessfully generated the c++ executable and the python wrapper, and I can run the generator to render the zebrapose annotated images

python3 generate_training_labels_for_BOP.py --bop_path /home/user/datasets/bop/ --dataset_name myDataset --force_rewrite True --is_training_data False --data_folder test --start_obj_id 0 --end_obj_id 1

The script runs fine and I can see that correct images are being generated, see the following screenshot:

Screenshot


However, when I open the saved images, all of them have some artifacts on the top border, and the rendered image content is shifted by the same height along the y axis. See this example:

Saved Image


My specs:

• Ubuntu 20.04 LTS
• Python 3.6.15
• OpenGL 1.3.2
• glfw 3.3.2
• OpenCV 4.8.0
• glad was downloaded with the default settings (C/C++, OpenGL, compatibility profile)

Has anyone experienced a similar issue or a good guess what could be the issue? Thanks in advance!

[suyz526]

Hi Jonas,

Thanks for your interest, and sorry for the inconvenience. I think it is caused by some memory alignment problem. Can you try to remove L185 to L187 and compile the render again?

Best regards, Yongzhi

[jonashein]

Hi Yongzhi,

thanks for your fast reply. It indeed looks like some alignment issue. I tested your proposed change but unfortunately it did not change anything. The height of the artifact border is exactly 50px. I also checked the image sizes, and the image shown in the UI has a resolution of 1280x1030, whereas the saved image has the (correct) resolution of 1280x1080. I'm currently working my way through the code to understand what happens between rendering the image in the UI and storing said image as a file, as to find out where this 50px difference stems from. I'm not familiar with the OpenGL API though, so I'd be grateful for any hints.

[suyz526]

Hmmm, that's a little bit weird. I have never seen such cases.

We defined cv::Mat img(IMG_HEIGHT, IMG_WIDTH, CV_8UC3);. So in the Opencv Mat, it contains up to 1280x1030x3 values. Maybe you can put a breakpoint here, to check the shape of the Opencv matbefore saving it.

[yinguoxiangyi]

@jonashein, have you solved the issue? I have the same problem and could you please give me some help?

[yinguoxiangyi]

The issue may be due to that the rendering window is not totally displayed in monitor screen. The bottom part is not rendered, after flipped, it turns to top part.

[yinguoxiangyi]

@suyz526 do you have any suggestion about how to render hidden part as well?

[suyz526]

@suyz526 do you have any suggestion about how to render hidden part as well?

Hi!

Thanks for providing more information regarding this bug.

I don't know if this will be helpful: https://www.glfw.org/docs/latest/context.html#context_offscreen

It would be just adding glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); into the code.

[yinguoxiangyi]

Thank you very much. It now works.