Performance for loading JPEG images using EwLoadExternalBitmap.

Question

Hi.

 

I am trying to print JPEG image on the screen by implementing EwLoadExternBitmap function.

Using this link as an example, the JPEG image was decoded using LIBJPEG and outputted to the screen, but it is too slow to load the image.

So I want to print the image on the screen using the hardware JPEG decoder built into STM32F7xx.

I am referring to the example of the Discovery board project, but I don't understand it well.

If possible, can I get an example of printing JPEG images to ExternalBitmap using a hardware decoder on the STM32F7 board?

 

Thanks.

Answer 1

Hello,

good to hear that you already got libJPEG up and running based on the provided example. The documentation about extern bitmap interface provides all the necessary background information about loading an image from some external source.

Concerning the hardware JPEG decoder within STM32F7 let me refer to the example that is provided in the STM32CubeFirmware tree: STM32Cube_FW_F7_V1.16.0\Projects\STM32F769I_EVAL\Examples\JPEG\JPEG_DecodingUsingFs_Interrupt\Src

In principal this has to be used instead of libJPEG.

Unfortunately we do not have a ready-to-use example for this use-case. But I think based on the two mentioned examples it should be possible to bring that together.

We used the hardware JPEG decoder in the context of video (MJPEG) decoding - based on the example from STCubeFirmware.

Best regards,

Manfred.