Hi Rafael, Assuming you have your OpenCV camera frame object named image in BGR format (default for OpenCV) Here is how you can render it at high fps in Bloc (override *BlElement>>#* drawOnSpartaCanvas: aCanvas in a subclass)
surface := aSpartaCanvas bitmap fromBGR: image imageData extent: image width @ image height stride: image widthStep. aSpartaCanvas fill paint: surface; path: surface bounds; draw Cheers, Alex On Wed, 12 Jun 2019 at 22:39, Rafael Luque <rafael.luque.le...@gmail.com> wrote: > Hello, > > I'm experimenting with an integration between OpenCV and Pharo based on > uFFI. My native C library opens a video camera and captures frames for > detecting certain points (aka blobs) of interest for my use case. The data > for these frames are available to Pharo as uchar* inside a C struct. > > My issues came when I tried to render the video camera frames inside > Pharo. The C examples I developed for testing the shared library show > frames around 50-60 fps. However, the best I have got in Pharo is around > 15-20 fps. > > My first try consisted of writing an specific ImageReadWriter for the > OpenCV image format, so I can build a Form for each frame and render it > with Morphic. This way I can render the video camera in GTInspector, but at > a terrible 5-10 fps. > > The second try was to use Bloc to render the Forms. I though the Moz2D > backend will provider better performance. Indeed, I got around 15-20 fps, > but it is still insufficient for playing video smoothly. > > My current try consist of using BlExternalForm to avoid all the frame data > processing inside Pharo, but I'm finding problems to render this kind of > "shallow" Forms using Bloc. > > I've also find some old mails (2017) about Clément Bera working in games > based on Cairo + SDL. Should I explore this approach for video rendering? > > In summary, I don't know what is the recommended approach (if any) to show > a sequence of video frames with decent bit-rate. > > Thank you! >
