An 'embedded-friendly' (aka Arduino) JPEG image encoding library

Hi, Very nice project. I wonder if it could support very low quality 4:2:0 jpeg encoding. I'm going to compress 320x200 rgb frame, to size below 3kB. I know that's crazy :) It's because I'm author of free available system to control unamed RC planes, called Qczek LRS. and i'm going to add experimental support for slow video transmission over a LoRa link. It would be something like 1-2fps 320x200 but it would be cool to make it possible using limited and very small and cheap hardware... Just going to connect SPI capable cammera, encode it's tream and send ... What do you think? Kris

You can find out more at the project site https://qczek.beyondrc.com/qczek-lrs-433mhz-1w-lora-rc-link/ Thank you in advance Kris

Is there a way to pipe the output from PNGdec to this library?
I'm looking for a way to covert a PNG image on an SD card to JPEG and your libraries seem to be the right tools to use. I'd appreciate it if you could point me to the right direction, thanks.

Into JPEGFixQuantE(), the memcpy() is redundant. Actually, the sTemp[] array can be used directly in later calculation without affecting the results into pJPEG->sQuantTable[].

Hey! First of all, thanks for the code.

I have been trying to encode and decode JPEG using this library on the Portenta H7:

• GrayScale image from a camera is stored in 76800 bytes (320 * 240 * 1) array.
• Image is compressed...

int compress() {
  rc = jpg.open(ucTemp, sizeof(ucTemp));

  if (rc != JPEG_SUCCESS) {
    return -1;
  }

  rc = jpg.encodeBegin(&jpe, WIDTH, HEIGHT, JPEG_PIXEL_GRAYSCALE, JPEG_SUBSAMPLE_444, JPEG_Q_BEST);
  if (rc != JPEG_SUCCESS) {
    Serial.print("Failed with the code: " );
    Serial.println(rc);
    return -1;
  }
  
  iMCUCount = ((WIDTH + jpe.cx-1)/ jpe.cx) * ((HEIGHT + jpe.cy-1) / jpe.cy);
  for (int i = 0; i < iMCUCount; i++) {
    rc = jpg.addMCU(&jpe, fb_in.getBuffer(), WIDTH);
    if (rc != JPEG_SUCCESS) {
      Serial.print("Failed with the code: " );
      Serial.println(rc);
      return -1;     
    }
  }
  iDataSize = jpg.close();
  return iDataSize;
}

Where fb_inis the object holding the 76k800 bytes of the camera image. The WIDTH is set to 320 and the HEIGHT to 240.

The compression returns no error, but then I send the data over the serial port to a python console and when I try to decode the JPEG and show the image, I get this:

https://imgur.com/a/qid6YCi

Here is a bit of the pythons code:

from PIL import Image
from io import BytesIO

(... some serial port stuff .. )

sizeOfTheImage = serialPort.readline()
receivedBytes = serialPort.read(int(sizeOfTheImage))

image = Image.open(BytesIO(receivedBytes))
image.show()