Const uint8_t asked, how to display an image which may vary?

Projects Programming
13

if you don't modify the data, you don't need to copy it in memory, instead you could keep a pointer to the data

here is an example:

const uint8_t aFlashBitmap1[] PROGMEM = {151, 146, 242, 146, 151,  0, 170, 85}; // 8x8 bitmap
const uint8_t aFlashBitmap2[] PROGMEM = {174, 170,  74,  74,  78,  0, 170, 85}; // 8x8 bitmap
const size_t aFlashBitmapSize = sizeof aFlashBitmap1;

const uint8_t * logo;

void dumpData() {
  Serial.print("Current LOGO : ");
  for (size_t i = 0; i < aFlashBitmapSize; i++) {
    Serial.print(pgm_read_byte(logo + i));
    Serial.write(' ');
  }
  Serial.println();
}


void setup() {
  Serial.begin(115200); Serial.println();

  logo = aFlashBitmap1;
  dumpData();

  logo = aFlashBitmap2;
  dumpData();
}

void loop() {}

the logo pointer will be first pointing at aFlashBitmap1 and then at aFlashBitmap2.
➜ This way you don't have a memory impact besides keeping a few pointers around. It's way more efficient.

you could also have a 2D array indexed by the page number for the pointers, so this way you would just do

tft.drawBitmap(30, 30,  logos[brand][0], 64, 64, BLACK,  WHITE);
tft.drawBitmap(30, 150,  logos[brand][1], 64, 64, BLACK,  WHITE);`

and no messing around with the ifs