JPEG_functions.ino

/*====================================================================================
  This sketch contains support functions to render the Jpeg images.

  Created by Bodmer 15th Jan 2017
  ==================================================================================*/

// Return the minimum of two values a and b
#define minimum(a,b)     (((a) < (b)) ? (a) : (b))

//====================================================================================
//   Opens the image file and prime the Jpeg decoder
//====================================================================================
void drawJpeg(const char *filename, int xpos, int ypos) {

  Serial.println("===========================");
  Serial.print("Drawing file: "); Serial.println(filename);
  Serial.println("===========================");

  // Open the named file (the Jpeg decoder library will close it after rendering image)
  fs::File jpegFile = SPIFFS.open( filename, "r");    // File handle reference for SPIFFS
  //  File jpegFile = SD.open( filename, FILE_READ);  // or, file handle reference for SD library

  if ( !jpegFile ) {
    Serial.print("ERROR: File \""); Serial.print(filename); Serial.println ("\" not found!");
    return;
  }

  // Use one of the three following methods to initialise the decoder:
  //boolean decoded = JpegDec.decodeFsFile(jpegFile); // Pass a SPIFFS file handle to the decoder,
  //boolean decoded = JpegDec.decodeSdFile(jpegFile); // or pass the SD file handle to the decoder,
  boolean decoded = JpegDec.decodeFsFile(filename);  // or pass the filename (leading / distinguishes SPIFFS files)
  // Note: the filename can be a String or character array type
  if (decoded) {
    // print information about the image to the serial port
    jpegInfo();

    // render the image onto the screen at given coordinates
    jpegRender(xpos, ypos);
  }
  else {
    Serial.println("Jpeg file format not supported!");
  }
}

//====================================================================================
//   Decode and render the Jpeg image onto the TFT screen
//====================================================================================
void jpegRender(int xpos, int ypos) {

  // retrieve infomration about the image
  uint16_t  *pImg;
  uint16_t mcu_w = JpegDec.MCUWidth;
  uint16_t mcu_h = JpegDec.MCUHeight;
  uint32_t max_x = JpegDec.width;
  uint32_t max_y = JpegDec.height;

  // Jpeg images are draw as a set of image block (tiles) called Minimum Coding Units (MCUs)
  // Typically these MCUs are 16x16 pixel blocks
  // Determine the width and height of the right and bottom edge image blocks
  uint32_t min_w = minimum(mcu_w, max_x % mcu_w);
  uint32_t min_h = minimum(mcu_h, max_y % mcu_h);

  // save the current image block size
  uint32_t win_w = mcu_w;
  uint32_t win_h = mcu_h;

  // record the current time so we can measure how long it takes to draw an image
  uint32_t drawTime = millis();

  // save the coordinate of the right and bottom edges to assist image cropping
  // to the screen size
  max_x += xpos;
  max_y += ypos;

  // read each MCU block until there are no more
  while ( JpegDec.readSwappedBytes()) { // Swap byte order so the SPI buffer can be used

    // save a pointer to the image block
    pImg = JpegDec.pImage;

    // calculate where the image block should be drawn on the screen
    int mcu_x = JpegDec.MCUx * mcu_w + xpos;  // Calculate coordinates of top left corner of current MCU
    int mcu_y = JpegDec.MCUy * mcu_h + ypos;

    // check if the image block size needs to be changed for the right edge
    if (mcu_x + mcu_w <= max_x) win_w = mcu_w;
    else win_w = min_w;

    // check if the image block size needs to be changed for the bottom edge
    if (mcu_y + mcu_h <= max_y) win_h = mcu_h;
    else win_h = min_h;

    // copy pixels into a contiguous block
    if (win_w != mcu_w)
    {
      uint16_t *cImg;
      int p = 0;
      cImg = pImg + win_w;
      for (int h = 1; h < win_h; h++)
      {
        p += mcu_w;
        for (int w = 0; w < win_w; w++)
        {
          *cImg = *(pImg + w + p);
          cImg++;
        }
      }
    }

    // draw image MCU block only if it will fit on the screen
    if ( ( mcu_x + win_w) <= tft.width() && ( mcu_y + win_h) <= tft.height())
    {
      tft.pushRect(mcu_x, mcu_y, win_w, win_h, pImg);
    }

    else if ( ( mcu_y + win_h) >= tft.height()) JpegDec.abort();

  }

  // calculate how long it took to draw the image
  drawTime = millis() - drawTime; // Calculate the time it took

  // print the results to the serial port
  Serial.print  ("Total render time was    : "); Serial.print(drawTime); Serial.println(" ms");
  Serial.println("=====================================");

}

//====================================================================================
//   Print information decoded from the Jpeg image
//====================================================================================
void jpegInfo() {

  Serial.println("===============");
  Serial.println("JPEG image info");
  Serial.println("===============");
  Serial.print  ("Width      :"); Serial.println(JpegDec.width);
  Serial.print  ("Height     :"); Serial.println(JpegDec.height);
  Serial.print  ("Components :"); Serial.println(JpegDec.comps);
  Serial.print  ("MCU / row  :"); Serial.println(JpegDec.MCUSPerRow);
  Serial.print  ("MCU / col  :"); Serial.println(JpegDec.MCUSPerCol);
  Serial.print  ("Scan type  :"); Serial.println(JpegDec.scanType);
  Serial.print  ("MCU width  :"); Serial.println(JpegDec.MCUWidth);
  Serial.print  ("MCU height :"); Serial.println(JpegDec.MCUHeight);
  Serial.println("===============");
  Serial.println("");
}

//====================================================================================
//   Open a Jpeg file and send it to the Serial port in a C array compatible format
//====================================================================================
void createArray(const char *filename) {

  // Open the named file
  fs::File jpgFile = SPIFFS.open( filename, "r");    // File handle reference for SPIFFS
  //  File jpgFile = SD.open( filename, FILE_READ);  // or, file handle reference for SD library

  if ( !jpgFile ) {
    Serial.print("ERROR: File \""); Serial.print(filename); Serial.println ("\" not found!");
    return;
  }

  uint8_t data;
  byte line_len = 0;
  Serial.println("");
  Serial.println("// Generated by a JPEGDecoder library example sketch:");
  Serial.println("// https://github.com/Bodmer/JPEGDecoder");
  Serial.println("");
  Serial.println("#include <pgmspace.h>");
  Serial.println("// Remove leading / from array name!");
  Serial.print  ("const uint8_t ");
  while (*filename != '.') Serial.print(*filename++);
  Serial.println("[] PROGMEM = {"); // PROGMEM added for AVR processors, it is ignored by Due

  while ( jpgFile.available()) {

    data = jpgFile.read();
    Serial.print("0x"); if (abs(data) < 16) Serial.print("0");
    Serial.print(data, HEX); Serial.print(",");// Add value and comma
    line_len++;
    if ( line_len >= 32) {
      line_len = 0;
      Serial.println();
    }

  }

  Serial.println("};\r\n");
  jpgFile.close();
}
//====================================================================================