bmpgen.html

---
layout: page
title: BMP generator
permalink: /bmpgen
---
<style>html {font-family: sans-serif}
.dotline {text-decoration:underline dotted}</style>
<textarea placeholder="paste your thing here" id="textinput" name="john"></textarea><br />
<label>or upload: <input type=file id="fileinput" name="george"/></label><br />
<button onclick="try {gen('text')} catch (e) {lyk('generation failure: ',e)}">generate from text</button>
<button onclick="try {gen('file')} catch (e) {lyk('generation failure: ',e)}">generate from file</button><br />
<a id="aoutput" name="rachel" download>output will go here</a><br />
<ul> options:
  <li><label>dimensions ([W,L])<input id="par1" name="larry" /></label></li>
  <li><label>resolution ([W,L])<input id="par2" name="jerry" /></label></li>
  <li><label>8-bit color array ([B,G,R,X] repeated 1-256 times)<input id="par3" name="garry" /></label></li>
  <li><label>force 8 bits<input type="checkbox" id="force8" name="joseph" /></label></li>
  <li><label for="rawmode" title="classic functionality - treats input as raw data rather than rgb data"><span class="dotline">raw mode</span></label>
  <input type="checkbox" checked id="rawmode" name="maria" /></li>
</ul>
<script>// baby
const lyk = (m,e) => {window.alert(m+e.message); throw e}
async function genfull(file, dims = null, res = [2835,2835], cca = null, f8 = false, raw = false) {
  // once upon a time, there was a boy
  const byte = ((base) => new Uint8Array(base.buffer))
  const feet = ((baby) => new Uint8Array([baby,baby>>8,baby>>16,baby>>24])) // unhappy birthday to you
  const bury = ((king) => new Uint8Array([king,king>>8])) // royal work of art
  if (file.size > 0xFFFFFFFF) {throw new RangeError("too much data")}
  if (file.size > 0xFFFFFAFF) {console.warn("this file is especially large. successful conversion cannot be guaranteed.")}
  else if (file.size > 0x7FFFFFFF) {console.warn("this file is very large. conversion may not work in certain environments.")}
  let bytes = new Uint8Array(await file.arrayBuffer()); if (!raw) {bytes.reverse()}
  let isz = bytes.byteLength/* no way in theyll im naming it is */; let bd
  switch (0) {
    case f8&&isz%3: bd=3;break
    case f8&&isz%2: bd=2;break
    default: bd = 1; if (cca?.length) {var c = new Uint8Array(cca)} else {var c = new Uint8Array(1024); for (let i = 0; i < 256; i++) {c.set([i,i,i,0],4*i)}}}
  try {let d = [...c]}
  catch {var c = new Uint8Array(0)}
  function getdivs(k) {const res = []; for (let i = 2; i <= Math.sqrt(k); i++) {if (k%i==0) {res.push(i)}}; return res}
  //function tohalf(a) {const res = []; for (let i = 0; i < 2; i++) {res.push(a.slice(i,Math.ceil(a.length/2)))}; return res}
  if (dims?.at(0) && dims?.at(1) && dims?.every(x => typeof x == 'number')) {var dim = dims.slice(0,2)}
  else {const ks = isz/bd; const hd = getdivs(ks).map(x=>ks/x)/*.reduce((a,v) => a*v,1)*/; var dim = [hd.at(-1),ks/hd.at(-1)]}
  const k=(bd==3?12:4); const bpr = k-bd*dim[0]%k;
  const p = new Uint8Array(bpr); const cc = c.byteLength
  isz += bpr*dim[1]; const o = 54+cc; const fs = isz+o;
  if (fs > 0xFFFFFFFF) {console.log(fs); throw new RangeError("file would be too large")}
  const Head1 = new Uint8Array([66,77,...feet(fs),0,0,0,0,...feet(o)])
  const Head2 = new Uint8Array([40,0,0,0,...feet(dim[0]),...feet(dim[1]),1,0,...bury(bd*8),0,0,0,0,...feet(isz),...feet(res[0]),...feet(res[1]),...feet(cc/4),0,0,0,0])
  // should mention dimensions are/were defined semi-arbitrarily due to operating from raw rgb
  const full = new Uint8Array(fs); console.log(Head1,Head2,bytes)
  full.set(Head1,0); full.set(Head2,14);
  full.set(c,54)
  for (let i = o, j = 0, k=0,row = new Array(dim[0]),rrow; k<dim[1]; i+=dim[0]+bpr,j+=dim[0],k++)
  {rrow = bytes.slice(j,j+dim[0]); for (let z = 0; z < dim[0]; z+=bd) {row[z/bd] = Array.from(rrow.slice(z,z+bd))};
   full.set(new Uint8Array(raw ? row.flat() : row.reverse().flat()),i); full.set(p,dim[0]+i)}
  // i'm so tired of trying so hard and not getting it right
  return full}
function gen(method) {
  if (method == 'text') {var ok = new File([document.getElementById('textinput').value],"johnresult.txt")}
  if (method == 'file') {var ok = document.getElementById('fileinput').files[0]}
  const pars = []; try {for (let i = 1,x; i <= 3; i++) {x = document.getElementById(`par${i}`).value; pars.push(x.length ? JSON.parse(x) : undefined)}}
  catch (e) {window.alert("error in param parsing: "+e.message); throw e}
  const chkcheck = (box) => document.getElementById(box).checked
  if (pars[2] != null && [pars[2].length%4,pars[2].length-3,1025-pars[2].length].some(x => x<=0)) {throw new SyntaxError('invalid color table')}
  const outer = document.getElementById('aoutput')
  try {genfull(ok,...pars,!chkcheck('force8'),chkcheck('rawmode')).then(fdata => outer.href = URL.createObjectURL(new Blob([fdata],{type:"image/bmp"}))).catch(e => console.error("something went issue",e))}
  catch (e) {window.alert("an error occured: "+e.message); throw e}
  Object.assign(outer,{download: ok.name.split(".").slice(0,-1).join(".").concat(".bmp"), innerHTML: "download output"})
  window.alert(`file ready for download. the output quality correlates to the input quality.`)}
</script>