Про генерацию картинок...

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>



enum{R,G,B,A};


void generate_tga(unsigned int width,unsigned int height, char* filename, unsigned char (*r)(int type,int x,int y,int w,int h),
                                                                          unsigned char (*g)(int type,int x,int y,int w,int h),
                                                                          unsigned char (*b)(int type,int x,int y,int w,int h),
                                                                          unsigned char (*a)(int type,int x,int y,int w,int h)) 
{
    char *  i  = malloc(sizeof(char) * ((width*height) * 4));
    //pre
    for(int x = 0; x < width; x++)
    for(int y = 0; y < height; y++)
    {
      i[x * 4 + y * width * 4 + 0] = r(R,x,y,width,height);
      i[x * 4 + y * width * 4 + 1] = g(G,x,y,width,height);
      i[x * 4 + y * width * 4 + 2] = b(B,x,y,width,height);
      i[x * 4 + y * width * 4 + 3] = a(A,x,y,width,height);
    }

  unsigned char xa= width % 256;
  unsigned char xb= (width-xa)/256;
  unsigned char ya= height % 256;
  unsigned char yb= (height-ya)/256;
  unsigned char header[18] = {0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, xa, xb, ya, yb, 32, 0};

  FILE * file = fopen(filename, "wb");
  assert(file);
  fwrite(header,1, sizeof(header), file);

  fwrite(i,1, width * height * 4, file);
  fclose(file);
  free(i);
  
}


unsigned char gen0(int type,int x,int y,int w ,int h)
{
    switch (type) {
        case R:return x+y%255 ;
        case G:return x-y%255 ;
        case B:return x-y%255 ;
        case A:return x+y%255 ;
        default: return 0;
    }
    return 0;
}


unsigned char gen1(int type,int x,int y,int w ,int h)
{

    srandom(x+y);

    switch (type) {
        case R:return (char)(x+y) + (char)(random())  % 255 ;
        case G:return (char)(x-y) + (char)(random())  % 255 ;
        case B:return (char)(x-x) + (char)(random())  % 255 ;
        case A:return (char)(y+y) + (char)(random())  % 255 ;
        default: return 0;
    }
    return 0;
}

unsigned char gen2(int type,int x,int y,int w ,int h)
{

    srandom(x);

    x =x+ random()%w;
    y =y- random()%h;
    // if(xx == x)
    {

    switch (type) {
        case R:return (char)(x+y) + (char)(random()) *x  % 255 ;
        case G:return (char)(y+x) + (char)(random())  % 255 ;
        case B:return (char)(x+x) + (char)(random())  % 255 ;
        case A:return (char)(y+y) + (char)(random())  % 255 ;
        default: return 0;
    }
    }
    return 0;
}


unsigned char gen3(int type,int x,int y,int w ,int h)
{

    srandom(x);

    if(x << y  ){

    switch (type) {
        case R:return x-y & y ;
        case G:return y+x & x ;
        case B:return w-y & x ;
        case A:return h+x & y ;
        default: return 0;
    }
    }
    return 0;
}

unsigned char gen4(int type,int x,int y,int w ,int h)
{
    static int pp = 0;
     int r = 100;
    int px = 100-pp++;
    int py = 100-pp++;


    if((x < px+r && x > px-r) && ( y < py+r && y > py-r) )
    {
        return 255;
    }

    return 0;
}

int main(int argc, char *argv[])
{

    generate_tga(800,600,"img-out0.tga",gen0,gen0,gen0,gen0);

    generate_tga(800,600,"img-out1.tga",gen1,gen1,gen1,gen1);

    generate_tga(800,600,"img-out2.tga",gen2,gen2,gen2,gen2);

    generate_tga(800,600,"img-out3.tga",gen3,gen3,gen3,gen3);



    return 0;
}

0:00:24.901781
0:00:25.444802

from PIL import Image
import sympy
import random
from datetime import datetime

start_time = datetime.now()
x = 3840  # разрешение по оси x
y = 2160  # разрешение по оси y
background_color = (0, 0, 0, 255)  # цвет фона RGBA
front_color = (109, 167, 65, 255)  # цвет рисунка RGBA
shift_x = random.randint(0, 10000)  # сдвиг по оси x
shift_y = random.randint(0, 10000)  # сдвиг по оси y
im = Image.new('RGBA', (x, y))  # создание "пустой" картинки в RGBA формате
for i in range(0, y):
    for j in range(0, x):
        if sympy.isprime((j + shift_x) ^ (i + shift_y)):
            im.putpixel((j, i), front_color)
        else:
            im.putpixel((j, i), background_color)
im.save(f'img_x{shift_x}_y{shift_y}.png')  # сохранение картинки
print(datetime.now() - start_time)

from PIL import Image
import sympy
import random
from datetime import datetime
import numpy as np

start_time = datetime.now()
x = 3840  # разрешение по оси x
y = 2160  # разрешение по оси y
background_color = np.array([0, 0, 0, 255], dtype='uint8')  # цвет фона RGBA
front_color = np.array([109, 167, 65, 255], dtype='uint8')  # цвет рисунка RGBA
shift_x = random.randint(0, 10000)  # сдвиг по оси x
shift_y = random.randint(0, 10000)  # сдвиг по оси y
image_pixels = np.tile(background_color, (y, x, 1))
for i in range(0, x):
    for j in range(0, y):
        if sympy.isprime((i + shift_x) ^ (j + shift_y)):
            image_pixels[j, i] = front_color
im = Image.fromarray(image_pixels)
im.save(f'img_x{shift_x}_y{shift_y}.png')  # сохранение картинки
print(datetime.now() - start_time)

0:00:17.416809

from PIL import Image
import sympy
import math

x = 1600
y = 900
scale = 1e-2
count = 100000
background_color = (0, 0, 0, 255)
front_color = (109, 167, 65, 255)
im = Image.new('RGBA', (x, y), background_color)

for i in range(0, count):
    ix = int(i * math.cos(i) * scale + x / 2)  # Magic.
    iy = int(i * math.sin(i) * scale + y / 2)  # More magic.
    if 0 <= ix and ix < x and 0 <= iy and iy < y and sympy.isprime(i):
        im.putpixel((ix, iy), front_color)

im.save('img.png')

--- img.py	2020-05-20 15:54:20.351282954 +0300
+++ img.py	2020-05-20 15:54:05.911254583 +0300
@@ -12,9 +12,10 @@
 shift_x = random.randint(0, 10000)  # сдвиг по оси x
 shift_y = random.randint(0, 10000)  # сдвиг по оси y
 image_pixels = np.tile(background_color, (y, x, 1))
+prime = [sympy.isprime(i) for i in range(0, 2 * max(x + shift_x, y + shift_y) + 1)]
 for i in range(0, x):
     for j in range(0, y):
-        if sympy.isprime((i + shift_x) ^ (j + shift_y)):
+        if prime[(i + shift_x) ^ (j + shift_y)]:
             image_pixels[j, i] = front_color
 im = Image.fromarray(image_pixels)
 im.save(f'img_x{shift_x}_y{shift_y}.png')  # сохранение картинки