Stap 9: Hoe om een lijn te tekenen?
Als we eenmaal een pixel-functie, kunnen we het gebruiken om te tekenen van een lijn gedefinieerd door een begin- en eindpunt op de x- en y as op het scherm.
#include //Include Wire library for I2C communication#define HEIGHT 64 #define WIDTH 128 const int RST = 10; //Assign pin 10 for Reset int i; //Set variable i as integer static unsigned char array[1024]; //Buffer array void setup() { pin_init(); //Initialize pins initialize_OLED(); //Initialize screen memset(array, 0, sizeof(array)); //Initialize array with 0s line(0,63,0,31); //Draw line Flush(); //Send data } void loop() { } void pin_init(){ Serial.begin(9600); //Set baud for serial transmission pinMode(RST, OUTPUT); //Set RST as output } void initialize_OLED(){ Wire.begin(); //Initialize I2C interface digitalWrite(RST, LOW); //Set RST pin low delay(100); //Wait 100 ms digitalWrite(RST, HIGH); //Set RST pin high Wire.beginTransmission(0x3D); // Start communication with slave Wire.write(0x00); //Command stream Wire.write(0xAE); //Set display Off Wire.write(0xD5); //Set display clock divide ratio/oscillator frequency Wire.write(0x80); Wire.write(0xA8); //Set multiplex ratio Wire.write(0x3F); Wire.write(0xD3); //Set display offset Wire.write(0x00); Wire.write(0x40); //Set display start line Wire.write(0x8D); //Set charge pump Wire.write(0x14); //VCC generated by internal DC/DC circuit Wire.write(0xA1); //Set segment re-map Wire.write(0xC0); //Set COM output scan direction Wire.write(0xDA); //Set COM pins hardware configuration Wire.write(0x12); Wire.write(0x81); //Set contrast control Wire.write(0xCF); Wire.write(0xD9); //Set pre-changed period Wire.write(0xF1); Wire.write(0xDB); //Set VCOMH Deselected level Wire.write(0x40); Wire.write(0xA4); //Set entire display on/off Wire.write(0xA6); //Set normal/inverse display Wire.write(0x20); //Set memory address mode Wire.write(0x00); //Horizontal Wire.write(0xAF); //Set display on Wire.endTransmission(); //End communicaiton with slave } /*Bresenham's line drawing algorithm*/ void line(int x1, int x2, int y1, int y2){ int cx = x1; int cy = y1; int dx = x2-cx; int dy = y2-cy; if(dx<0){ dx = 0-dx; } if(dy<0){ dy = 0-dy; } int sx = 0; int sy = 0; if(cx(0-dy)){ err = err-dy; cx = cx+sx; } if(e2=WIDTH) || (y<0) || (y>=HEIGHT)){ //Check for boundaries return; } else{ array[x+(y/8)*WIDTH] |= _BV((y%8)); //Store pixel in array } } void Flush(){ Wire.beginTransmission(0x3D); //Start communication with slave Wire.write(0x00); //Command stream Wire.write(0x00); //Set lower column start address for page addressing mode Wire.write(0x10); //Set higher column start address for page addressing mode Wire.write(0x40); //Set display start line Wire.endTransmission(); //End communication with slave unsigned char twbrbackup = TWBR; //Two wire bit rate register TWBR = 12; //Set to 400 kHz for(unsigned short q=0; q<(WIDTH*HEIGHT/8); q++){ Wire.beginTransmission(0x3D); //Start communication with slave Wire.write(0x40); //Data stream for(unsigned char w=0; w<16; w++){ Wire.write(array[q]); //Transmit data to be displayed q++; } q--; Wire.endTransmission(); //End communication with slave } TWBR = twbrbackup; } De functie regel is gebaseerd op het Bresenham van lijntekening algoritme gebruikt bij het tekenen van lijnen met pixels. De volgende pseudocode werd gebruikt om het algoritme in ons programma:
http://41j.com/blog/2012/09/bresenhams-line-drawin...
Dit algoritme in principe vult de pixels tussen (x 0, y0) en (x1, y1) door te beslissen welke pixels moeten worden ingeschakeld in volgende gebaseerd op een foutwaarde. Raadpleeg de volgende koppelingen voor meer informatie over het algoritme:
http://www.cs.Helsinki.fi/Group/Goa/mallinnus/line...
https://en.wikipedia.org/wiki/Bresenham%27s_line_a...
