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//! Render one page with the pure-Rust renderer and, when installed, the
//! docling-parse shim, and write both plus a difference image:
//!
//! cargo run -q -p docling-pdf --example render_compare -- file.pdf PAGE SCALE OUT_STEM
//!
//! Writes `OUT_STEM.rust.png`, `OUT_STEM.shim.png`, `OUT_STEM.diff.png` and
//! prints the mean absolute difference.
fn main() {
let args: Vec<String> = std::env::args().collect();
if args.len() < 5 {
eprintln!("usage: render_compare file.pdf PAGE SCALE OUT_STEM");
std::process::exit(2);
}
let bytes = std::fs::read(&args[1]).expect("read pdf");
let page: usize = args[2].parse().expect("page");
let scale: f64 = args[3].parse().expect("scale");
let stem = &args[4];
if std::env::var_os("DOCLING_RS_RENDER_DUMP").is_some() {
dump(&bytes, page);
}
if let Ok(ids) = std::env::var("DOCLING_RS_RENDER_OBJ") {
if let Ok(doc) = lopdf::Document::load_mem(&bytes) {
for id in ids.split(',').filter_map(|s| s.trim().parse::<u32>().ok()) {
match doc.get_object((id, 0)) {
Ok(lopdf::Object::Stream(s)) => {
let mut d = s.dict.clone();
d.remove(b"Length");
eprintln!("obj {id}: stream {d:?}");
if let Ok(c) = s.decompressed_content() {
let text = String::from_utf8_lossy(&c[..c.len().min(600)]);
eprintln!(
" content ({} bytes): {}",
c.len(),
text.replace('\n', " ")
);
}
}
Ok(o) => eprintln!("obj {id}: {o:?}"),
Err(e) => eprintln!("obj {id}: {e}"),
}
}
}
}
let meta = docling_pdf::pdf_meta::PdfMeta::open(&bytes).expect("lopdf open");
let t = std::time::Instant::now();
let rust = docling_pdf::render::render_page(&meta, page - 1, scale).expect("rust render");
eprintln!(
"rust: {}x{} in {:?}",
rust.width(),
rust.height(),
t.elapsed()
);
rust.save(format!("{stem}.rust.png")).unwrap();
if let Some(dp) = docling_pdf::dparse_render::Doc::open_if_enabled(&bytes, None) {
let t = std::time::Instant::now();
let shim = dp.render(page - 1, scale, 1.0).expect("shim render");
eprintln!(
"shim: {}x{} in {:?}",
shim.width(),
shim.height(),
t.elapsed()
);
shim.save(format!("{stem}.shim.png")).unwrap();
if shim.dimensions() == rust.dimensions() {
let mut diff = image::RgbImage::new(rust.width(), rust.height());
let mut sum = 0u64;
for (d, (a, b)) in diff.pixels_mut().zip(rust.pixels().zip(shim.pixels())) {
let mut m = 0u8;
for c in 0..3 {
let v = (i32::from(a[c]) - i32::from(b[c])).unsigned_abs() as u8;
sum += u64::from(v);
m = m.max(v);
}
*d = image::Rgb([255 - m, 255 - m, 255]);
}
diff.save(format!("{stem}.diff.png")).unwrap();
println!(
"mean |Δ| = {:.3}",
sum as f64 / (rust.as_raw().len() as f64)
);
} else {
println!(
"size mismatch: rust {:?} shim {:?}",
rust.dimensions(),
shim.dimensions()
);
}
}
docling_pdf::timing::report();
}
/// `DOCLING_RS_RENDER_DUMP=1`: print the page's operator histogram and its
/// first operators, to see what a blank render skipped.
#[allow(dead_code)]
fn dump(bytes: &[u8], page: usize) {
let Ok(doc) = lopdf::Document::load_mem(bytes) else {
return;
};
let mut pages: Vec<_> = doc.get_pages().into_iter().collect();
pages.sort_by_key(|(n, _)| *n);
let Some((_, pid)) = pages.get(page - 1) else {
return;
};
let content = doc.get_page_content(*pid);
let Ok(ops) = lopdf::content::Content::decode(&content) else {
eprintln!("content undecodable");
return;
};
let mut hist = std::collections::BTreeMap::<String, usize>::new();
for op in &ops.operations {
*hist.entry(op.operator.clone()).or_default() += 1;
}
eprintln!("ops: {hist:?}");
for op in ops.operations.iter().take(80) {
eprintln!(" {} {:?}", op.operator, op.operands);
}
// `DOCLING_RS_RENDER_OPS=Do`: every occurrence of that operator with the
// six operators before it.
if let Ok(want) = std::env::var("DOCLING_RS_RENDER_OPS") {
for (i, op) in ops.operations.iter().enumerate() {
if op.operator == want {
let start = i.saturating_sub(6);
let ctx: Vec<String> = ops.operations[start..=i]
.iter()
.map(|o| format!("{} {:?}", o.operator, o.operands))
.collect();
eprintln!("… {}", ctx.join(" | "));
}
}
}
if let Ok((res, ids)) = doc.get_page_resources(*pid) {
let res = res.or_else(|| ids.first().and_then(|id| doc.get_dictionary(*id).ok()));
if let Some(res) = res {
let mut r = res.clone();
let fonts = r.remove(b"Font");
let xobjs = r.remove(b"XObject");
eprintln!("resources: {r:?}");
if let Some(xo) = xobjs {
let deref = |o: &lopdf::Object| -> lopdf::Object {
match o {
lopdf::Object::Reference(id) => {
doc.get_object(*id).cloned().unwrap_or(lopdf::Object::Null)
}
o => o.clone(),
}
};
if let lopdf::Object::Dictionary(xd) = deref(&xo) {
for (name, x) in xd.iter() {
if let lopdf::Object::Stream(s) = deref(x) {
let mut d = s.dict.clone();
d.remove(b"Length");
eprintln!(
"xobject /{} ({:?}): {:?}",
String::from_utf8_lossy(name),
x,
d
);
// JPEG markers: SOF component count, APP14 Adobe transform.
let raw = &s.content;
let mut i = 2;
while i + 4 <= raw.len() && raw[i] == 0xFF {
let m = raw[i + 1];
let len = usize::from(raw[i + 2]) << 8 | usize::from(raw[i + 3]);
if m == 0xEE && raw.len() > i + 15 {
eprintln!(
" APP14 {:?} transform {}",
std::str::from_utf8(&raw[i + 4..i + 9]).unwrap_or("?"),
raw[i + 15]
);
}
if (0xC0..=0xCF).contains(&m) && m != 0xC4 && m != 0xC8 && m != 0xCC
{
eprintln!(" SOF{} components {}", m - 0xC0, raw[i + 9]);
break;
}
if m == 0xDA {
break;
}
i += 2 + len;
}
for key in ["SMask", "Mask", "ColorSpace"] {
if let Ok(v) = d.get(key.as_bytes()) {
if let lopdf::Object::Stream(ms) = deref(v) {
let mut md = ms.dict.clone();
md.remove(b"Length");
eprintln!(" {key}: {md:?}");
} else if let lopdf::Object::Array(a) = deref(v) {
eprintln!(" {key}: {a:?}");
}
}
}
}
}
}
}
if let Some(fonts) = fonts {
let deref = |o: &lopdf::Object| -> lopdf::Object {
match o {
lopdf::Object::Reference(id) => {
doc.get_object(*id).cloned().unwrap_or(lopdf::Object::Null)
}
o => o.clone(),
}
};
if let lopdf::Object::Dictionary(fd) = deref(&fonts) {
for (name, f) in fd.iter() {
let f = deref(f);
eprintln!("font /{}: {:?}", String::from_utf8_lossy(name), f);
if let lopdf::Object::Dictionary(d) = &f {
for key in ["FontDescriptor", "DescendantFonts", "Encoding"] {
if let Ok(v) = d.get(key.as_bytes()) {
let v = deref(v);
let v = match v {
lopdf::Object::Array(a) => {
a.first().map(deref).unwrap_or(lopdf::Object::Null)
}
v => v,
};
let short = format!("{v:?}");
eprintln!(" {key}: {}", &short[..short.len().min(600)]);
if let lopdf::Object::Dictionary(dd) = &v {
for ff in ["FontFile", "FontFile2", "FontFile3"] {
if let Ok(s) = dd.get(ff.as_bytes()) {
if let lopdf::Object::Stream(st) = deref(s) {
let data = st
.decompressed_content()
.unwrap_or_default();
eprintln!(
" {ff}: {:?} {} bytes, head {:?}",
st.dict.get(b"Subtype").ok(),
data.len(),
&data[..data.len().min(16)]
);
}
}
}
}
}
}
}
}
}
}
}
}
}