Yan Wang

I build browser-side tools where the file never leaves the tab — canvas, workers and WASM instead of an upload endpoint. Currently lensup.ai, a document scanner running in 20 languages.

Joined on Sep 13, 2026 https://lensup.ai/

Work

Independent — building browser-side web tools

Yan Wang

Nov 2

When a PDF Export Turns Every Page Into a Picture, Define the Text Contract First

#testing #softwareengineering

3 min read

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Yan Wang

Nov 2

A PDF Cover Needs More Than a Screenshot as Its Test Oracle

#testing #softwareengineering

3 min read

Yan Wang

Nov 1

Report missing and repeated pages in a PDF split plan

#javascript #testing

3 min read

Yan Wang

Nov 1

Parse a page selection completely or not at all

#javascript #testing

3 min read

Yan Wang

Oct 31

Test a JPG Name Collision Policy With Executable Examples

#unicode #javascript #testing

3 min read

Yan Wang

Oct 30

Count OOXML Payload Bytes Without Pretending to Predict Compression

#javascript #testing

3 min read

Yan Wang

Oct 29

Plan EPUB Reading Order From the Spine, Not ZIP Filenames

#javascript #testing #node

4 min read

Yan Wang

Oct 28

A contain rectangle is a contract, not a PDF fidelity test

#javascript #testing

3 min read

Yan Wang

Oct 27

A Centimeter-to-Pixel Contract With Explicit Limits

#javascript

3 min read

Yan Wang

Oct 26

Validate a PDF reorder as a permutation before you test the export

#javascript #testing

3 min read

Yan Wang

Oct 25

Test PDF merge navigation separately from page order

#python #testing #pdf #abotwrotethis

6 min read

Yan Wang

Oct 25

Test OCR text and Markdown structure separately with a small token check

#javascript #testing #markdown #abotwrotethis

4 min read

Yan Wang

Oct 24

Page positions, page labels, and printed numbers are different PDF data

#pdf #abotwrotethis #python

4 min read

Yan Wang

Oct 23

A PDF merge can preserve mixed page sizes: verify the download, not the thumbnails

#pdf #testing #abotwrotethis

4 min read

Yan Wang

Oct 22

300 DPI means four times the pixels: budget your canvas before rendering a PDF

#javascript #webdev #performance #abotwrotethis

4 min read

Yan Wang

Sep 13

60 % of our image decode failures were HEIC files named .jpg

#javascript #webdev #debugging #images

6 min read

Yan Wang

Sep 13

A scan is never perfectly square

#javascript #webdev #canvas #graphics

6 min read

Yan Wang

Sep 13

The adaptive threshold that deleted the thing we were looking for

#javascript #webdev #algorithms #computervision

5 min read

Yan Wang

Sep 13

Three things that bit us moving a document scanner fully into the browser

#javascript #webdev #privacy #performance

6 min read

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Yan Wang

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When a PDF Export Turns Every Page Into a Picture, Define the Text Contract First

Want to connect with Yan Wang?

A PDF Cover Needs More Than a Screenshot as Its Test Oracle

Report missing and repeated pages in a PDF split plan

Parse a page selection completely or not at all

Test a JPG Name Collision Policy With Executable Examples

Count OOXML Payload Bytes Without Pretending to Predict Compression

Plan EPUB Reading Order From the Spine, Not ZIP Filenames

A contain rectangle is a contract, not a PDF fidelity test

A Centimeter-to-Pixel Contract With Explicit Limits

Validate a PDF reorder as a permutation before you test the export

Test PDF merge navigation separately from page order

Test OCR text and Markdown structure separately with a small token check

Page positions, page labels, and printed numbers are different PDF data

A PDF merge can preserve mixed page sizes: verify the download, not the thumbnails

300 DPI means four times the pixels: budget your canvas before rendering a PDF

60 % of our image decode failures were HEIC files named .jpg

A scan is never perfectly square

The adaptive threshold that deleted the thing we were looking for

Three things that bit us moving a document scanner fully into the browser