--- title: Why are all the amount values negative? | daily.dev description: A bank statement PDF was producing all-negative amounts during conversion. Investigation using PDFSnake revealed that the PDF uses trailing minus signs for... canonical: https://daily.dev/posts/why-are-all-the-amount-values-negative--mftiohd3l twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Why are all the amount values negative? | daily.dev og:description: A bank statement PDF was producing all-negative amounts during conversion. Investigation using PDFSnake revealed that the PDF uses trailing minus signs for... og:url: https://daily.dev/posts/why-are-all-the-amount-values-negative--mftiohd3l og:image: https://api.daily.dev/og/posts/mFtiohd3l.png og:image:alt: Why are all the amount values negative? og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Why are all the amount values negative? **[Hacker News](https://daily.dev/sources/hn)** · 3 min read · 0 upvotes · 0 comments ## Summary A bank statement PDF was producing all-negative amounts during conversion. Investigation using PDFSnake revealed that the PDF uses trailing minus signs for alignment, and hides the minus sign on positive values by rendering it in the same grey color as the background (grey level 0.878). Two solutions are proposed: using OCR on rasterized PNG images (slower, less accurate) or stripping out non-black text elements during extraction (requires storing text color during parsing). ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why would a PDF text extractor read a positive dollar amount as negative? Some PDFs encode a trailing minus sign character after positive amounts but set its grey level to match the background color, rendering it invisible to a human reader while still present in the underlying text stream. A parser that reads raw text commands (BT, Tj, g) picks up that hidden minus sign and interprets the value as negative, even though nothing looks wrong visually. _Anyone building PDF data extraction pipelines can find similar parsing edge cases discussed on daily.dev._ ### How can I fix a PDF parser that misreads amounts due to invisible characters? Two approaches work: convert the PDF pages to images and run OCR software, which sidesteps hidden text encoding but is slower and less than 100% accurate; or track the grey level or color of each text element during extraction and strip out any text rendered in a color matching the background, treating it as invisible. The second approach requires storing color metadata that a basic text-extraction pipeline may not capture. _Developers debugging document-parsing edge cases can compare approaches like this on daily.dev._ ## Similar posts on daily.dev - [Redesigning Banking PDF Table Extraction: A Layered Approach with Java](https://daily.dev/posts/redesigning-banking-pdf-table-extraction-a-layered-approach-with-java-r4y6b8lpf) · InfoQ · 0 upvotes · 0 comments - [The Barren Fields](https://daily.dev/posts/the-barren-fields-kzfmhkc0b) · The Daily WTF · 0 upvotes · 0 comments - [10 years of personal finances in plain text files](https://daily.dev/posts/10-years-of-personal-finances-in-plain-text-files-uscnbakm1) · Hacker News · 0 upvotes · 0 comments --- Tags: [#machine-learning](https://daily.dev/tags/machine-learning) [View this post on daily.dev](https://daily.dev/posts/why-are-all-the-amount-values-negative--mftiohd3l) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Why are all the amount values negative?","url":"https://daily.dev/posts/why-are-all-the-amount-values-negative--mftiohd3l","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/why-are-all-the-amount-values-negative--mftiohd3l"},"datePublished":"2026-08-08T03:22:05.939Z","dateModified":"2026-09-13T20:57:04.631Z","description":"A bank statement PDF was producing all-negative amounts during conversion. 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A parser that reads raw text commands (BT, Tj, g) picks up that hidden minus sign and interprets the value as negative, even though nothing looks wrong visually. Anyone building PDF data extraction pipelines can find similar parsing edge cases discussed on daily.dev."}},{"@type":"Question","name":"How can I fix a PDF parser that misreads amounts due to invisible characters?","acceptedAnswer":{"@type":"Answer","text":"Two approaches work: convert the PDF pages to images and run OCR software, which sidesteps hidden text encoding but is slower and less than 100% accurate; or track the grey level or color of each text element during extraction and strip out any text rendered in a color matching the background, treating it as invisible. The second approach requires storing color metadata that a basic text-extraction pipeline may not capture. Developers debugging document-parsing edge cases can compare approaches like this on daily.dev."}}]} ```