I write a code who change a picture in Dithering,but show me a NullPointerException (line 16)
What can I do? I have update Processing 3.5.4:
This is coding:
//variable to store image
import processing.svg.*;
PImage theImageCarrier;
void setup(){
//size of the output window displaying the image
size(1100 ,512, SVG, "filename.svg");
//loading the image into the variable
theImageCarrier = loadImage("pics.jpg");
//theImageCarrier.filter(GRAY); //turning the image into gray scale
//displaying the image on the left half of output window
image(theImageCarrier,0,0); // here is NullPointerException
}
int index(int x, int y){
return x + y * theImageCarrier.width;
}
void draw() {
//before working on pixels u load them
theImageCarrier.loadPixels();
//look at all of the pixels
for(int y=0; y< theImageCarrier.height-1; y++)//all y values of the image
{
for(int x=1; x<theImageCarrier.width-1; x++) //all x values of the image
{
//look at a given pixel from the image
color pix = theImageCarrier.pixels[index(x,y)];
//pull out the red,green and blue value from the pixel
float oldR = red(pix);
float oldG = green(pix);
float oldB = blue(pix);
//factor is the number of colors available in your color palet
//using which u color your image.
//eg if factor = 1, then there are 2 possible values 0 and 1.
//Hence the number of colors in your color palet of each type ( ie R,G and B) are only 2.
int factor = 1;
//quantise the values to a shorter range of values
int newR = round(factor * oldR/255) * (255/factor);
int newG = round(factor * oldG/255) * (255/factor);
int newB = round(factor * oldB/255) * (255/factor);
//set it back to that pixel
theImageCarrier.pixels[index(x,y)] = color(newR,newG,newB);
//Dithering algo for pixel correction begins from here
//errors for each color after quantization
float errR = oldR - newR;
float errG = oldG - newG;
float errB = oldB - newB;
//case1
int index = index(x+1,y);
color c = theImageCarrier.pixels[index];
float r = red(c);
float g = green(c);
float b = blue(c);
//pass the error onto the current color and then update the pixels
r = r + errR * 7/16.0;
g = g + errG * 7/16.0;
b = b + errB * 7/16.0;
theImageCarrier.pixels[index] = color(r,g,b);
//case2
index = index(x-1,y+1);
c = theImageCarrier.pixels[index];
r = red(c);
g = green(c);
b = blue(c);
//pass the error onto the current color and then update the pixels
r = r + errR * 7/16.0;
g = g + errG * 7/16.0;
b = b + errB * 7/16.0;
theImageCarrier.pixels[index] = color(r,g,b);
//case3
index = index(x,y+1);
c = theImageCarrier.pixels[index];
r = red(c);
g = green(c);
b = blue(c);
//pass the error onto the current color and then update the pixels
r = r + errR * 3/16.0;
g = g + errG * 3/16.0;
b = b + errB * 3/16.0;
theImageCarrier.pixels[index] = color(r,g,b);
//case4
index = index(x+1,y+1);
c = theImageCarrier.pixels[index];
r = red(c);
g = green(c);
b = blue(c);
//pass the error onto the current color and then update the pixels
r = r + errR * 5/16.0;
g = g + errG * 5/16.0;
b = b + errB * 5/16.0;
theImageCarrier.pixels[index] = color(r,g,b);
//Dithering algo ends here
/*
pixel[x + 1][y ] := pixel[x + 1][y ] + quant_error * 7 / 16
pixel[x - 1][y + 1] := pixel[x - 1][y + 1] + quant_error * 3 / 16
pixel[x ][y + 1] := pixel[x ][y + 1] + quant_error * 5 / 16
pixel[x + 1][y + 1] := pixel[x + 1][y + 1] + quant_error * 1 / 16
*/
}
}
//after working you update the image pixels
theImageCarrier.updatePixels();
//quantized image on the right
image(theImageCarrier , 512,0);
}
