nx_png_lum.nx source

1// nx_png_lum.nx -- sovereign PNG mean-luminance probe over a content rectangle. Turns "the page looks dark" 2// into a NUMBER (mean luma 0..255) measured from the actual rendered pixels -- the "show proof not I can see" 3// tool for the S21 browser dogfood before/after. usage: nx_png_lum <file.png>. Samples y[100..h-40] x[60..w-40] 4// (skips the white browser chrome bar at top). license_tier: ORIGINAL 5import "nx_syscalls.nx" 6import "nx_png_decoder.nx" 7 8func hw(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} sys_write(1,s,n); return 0 } 9func pn(v: i64) -> i64 { let t: *u8=sys_mmap(24); var m: i64=v; if m<0{sys_write(1,"-" as *u8,1);m=0-m} var k: i64=0; if m==0{t[0]=48 as u8;k=1} while m>0{t[k]=(48+(m%10)) as u8;m=m/10;k=k+1} let b: *u8=sys_mmap(24); var j: i64=0; while j<k{b[j]=t[k-1-j];j=j+1} sys_write(1,b,k); return 0 } 10 11func main(argc: i64, argv: *i64) -> i64 { 12 if argc < 2 { hw("usage: nx_png_lum <file.png>\n" as *u8); sys_exit(2); return 2 } 13 let lb: *i64 = sys_mmap(16) as *i64 14 let buf: *u8 = sys_read_file(argv[1] as *u8, lb) 15 if (buf as i64) == 0 { hw("cannot read\n" as *u8); sys_exit(3); return 3 } 16 let res: *NxPngResult = nx_png_decode(buf, lb[0]) 17 if (res as i64) == 0 { hw("decode null\n" as *u8); sys_exit(4); return 4 } 18 if res.error_code != 0 { hw("decode err=" as *u8); pn(res.error_code); hw("\n" as *u8); sys_exit(5); return 5 } 19 let hdr: *NxPngHeader = res.header 20 let w: i64 = hdr.width 21 let h: i64 = hdr.height 22 let nc: i64 = res.n_channels 23 let px: *u8 = res.pixels 24 var y0: i64 = 100 25 var y1: i64 = h - 40 26 var x0: i64 = 60 27 var x1: i64 = w - 40 28 if y1 <= y0 { y0 = 0; y1 = h } 29 if x1 <= x0 { x0 = 0; x1 = w } 30 var sum: i64 = 0 31 var cnt: i64 = 0 32 var y: i64 = y0 33 while y < y1 { 34 var x: i64 = x0 35 while x < x1 { 36 let o: i64 = (y * w + x) * nc 37 let r: i64 = px[o] as i64 38 let g: i64 = px[o+1] as i64 39 let b: i64 = px[o+2] as i64 40 sum = sum + (r + g + b) / 3 41 cnt = cnt + 1 42 x = x + 1 43 } 44 y = y + 1 45 } 46 var mean: i64 = 0 47 if cnt > 0 { mean = sum / cnt } 48 hw("png " as *u8); hw(argv[1] as *u8); hw(" " as *u8); pn(w); hw("x" as *u8); pn(h); hw(" content mean-luma=" as *u8); pn(mean); hw("/255 " as *u8) 49 if mean < 90 { hw("(DARK theme)\n" as *u8) } else { hw("(LIGHT/white)\n" as *u8) } 50 sys_exit(0) 51 return 0 52}