Optical Character Recognition (OCR) turns images of text—scans, smartphone photos, PDFs—into machine-readable strings and, increasingly, structured data. Modern OCR is a pipeline that cleans an image, finds text, reads it, and exports rich metadata so downstream systems can search, index, or extract fields. Two widely used output standards are hOCR, an HTML microformat for text and layout, and ALTO XML, a library/archives-oriented schema; both preserve positions, reading order, and other layout cues and are supported by popular engines like Tesseract.
Preprocessing. OCR quality starts with image cleanup: grayscale conversion, denoising, thresholding (binarization), and deskewing. Canonical OpenCV tutorials cover global, adaptive and Otsu thresholding—staples for documents with nonuniform lighting or bimodal histograms. When illumination varies within a page (think phone snaps), adaptive methods often outperform a single global threshold; Otsu automatically picks a threshold by analyzing the histogram. Tilt correction is equally important: Hough-based deskewing (Hough Line Transform) paired with Otsu binarization is a common and effective recipe in production preprocessing pipelines.
Detection vs. recognition. OCR is typically split into text detection (where is the text?) and text recognition (what does it say?). In natural scenes and many scans, fully convolutional detectors like EAST efficiently predict word- or line-level quadrilaterals without heavy proposal stages and are implemented in common toolkits (e.g., OpenCV’s text detection tutorial). On complex pages (newspapers, forms, books), segmentation of lines/regions and reading order inference matter:Kraken implements traditional zone/line segmentation and neural baseline segmentation, with explicit support for different scripts and directions (LTR/RTL/vertical).
Recognition models. The classic open-source workhorse Tesseract (open-sourced by Google, with roots at HP) evolved from a character classifier into an LSTM-based sequence recognizer and can emit searchable PDFs, hOCR/ALTO-friendly outputs, and more from the CLI. Modern recognizers rely on sequence modeling without pre-segmented characters. Connectionist Temporal Classification (CTC) remains foundational, learning alignments between input feature sequences and output label strings; it’s widely used in handwriting and scene-text pipelines.
In the last few years, Transformers reshaped OCR. TrOCR uses a vision Transformer encoder plus a text Transformer decoder, trained on large synthetic corpora then fine-tuned on real data, with strong performance across printed, handwritten and scene-text benchmarks (see also Hugging Face docs). In parallel, some systems sidestep OCR for downstream understanding: Donut (Document Understanding Transformer) is an OCR-free encoder-decoder that directly outputs structured answers (like key-value JSON) from document images (repo, model card), avoiding error accumulation when a separate OCR step feeds an IE system.
If you want batteries-included text reading across many scripts, EasyOCR offers a simple API with 80+ language models, returning boxes, text, and confidences—handy for prototypes and non-Latin scripts. For historical documents, Kraken shines with baseline segmentation and script-aware reading order; for flexible line-level training, Calamari builds on the Ocropy lineage (Ocropy) with (multi-)LSTM+CTC recognizers and a CLI for fine-tuning custom models.
Generalization hinges on data. For handwriting, the IAM Handwriting Database provides writer-diverse English sentences for training and evaluation; it’s a long-standing reference set for line and word recognition. For scene text, COCO-Text layered extensive annotations over MS-COCO, with labels for printed/handwritten, legible/illegible, script, and full transcriptions (see also the original project page). The field also relies heavily on synthetic pretraining: SynthText in the Wild renders text into photographs with realistic geometry and lighting, providing huge volumes of data to pretrain detectors and recognizers (reference code & data).
Competitions under ICDAR’s Robust Reading umbrella keep evaluation grounded. Recent tasks emphasize end-to-end detection/reading and include linking words into phrases, with official code reporting precision/recall/F-score, intersection-over-union (IoU), and character-level edit-distance metrics—mirroring what practitioners should track.
OCR rarely ends at plain text. Archives and digital libraries prefer ALTO XML because it encodes the physical layout (blocks/lines/words with coordinates) alongside content, and it pairs well with METS packaging. The hOCR microformat, by contrast, embeds the same idea into HTML/CSS using classes like ocr_line and ocrx_word, making it easy to display, edit, and transform with web tooling. Tesseract exposes both—e.g., generating hOCR or searchable PDFs directly from the CLI (PDF output guide); Python wrappers like pytesseract add convenience. Converters exist to translate between hOCR and ALTO when repositories have fixed ingestion standards—see this curated list of OCR file-format tools.
The strongest trend is convergence: detection, recognition, language modeling, and even task-specific decoding are merging into unified Transformer stacks. Pretraining on large synthetic corpora remains a force multiplier. OCR-free models will compete aggressively wherever the target is structured outputs rather than verbatim transcripts. Expect hybrid deployments too: a lightweight detector plus a TrOCR-style recognizer for long-form text, and a Donut-style model for forms and receipts.
Tesseract (GitHub) · Tesseract docs · hOCR spec · ALTO background · EAST detector · OpenCV text detection · TrOCR · Donut · COCO-Text · SynthText · Kraken · Calamari OCR · ICDAR RRC · pytesseract · IAM handwriting · OCR file-format tools · EasyOCR
Optical Character Recognition (OCR) is a technology used to convert different types of documents, such as scanned paper documents, PDF files or images captured by a digital camera, into editable and searchable data.
OCR works by scanning an input image or document, segmenting the image into individual characters, and comparing each character with a database of character shapes using pattern recognition or feature recognition.
OCR is used in a variety of sectors and applications, including digitizing printed documents, enabling text-to-speech services, automating data entry processes, and assisting visually impaired users to better interact with text.
While great advancements have been made in OCR technology, it isn't infallible. Accuracy can vary depending upon the quality of the original document and the specifics of the OCR software being used.
Although OCR is primarily designed for printed text, some advanced OCR systems are also able to recognize clear, consistent handwriting. However, typically handwriting recognition is less accurate because of the wide variation in individual writing styles.
Yes, many OCR software systems can recognize multiple languages. However, it's important to ensure that the specific language is supported by the software you're using.
OCR stands for Optical Character Recognition and is used for recognizing printed text, while ICR, or Intelligent Character Recognition, is more advanced and is used for recognizing hand-written text.
OCR works best with clear, easy-to-read fonts and standard text sizes. While it can work with various fonts and sizes, accuracy tends to decrease when dealing with unusual fonts or very small text sizes.
OCR can struggle with low-resolution documents, complex fonts, poorly printed texts, handwriting, and documents with backgrounds that interfere with the text. Also, while it can work with many languages, it may not cover every language perfectly.
Yes, OCR can scan colored text and backgrounds, although it's generally more effective with high-contrast color combinations, such as black text on a white background. The accuracy might decrease when text and background colors lack sufficient contrast.
The JPEG 2000 Multi-layer (JPM) format is an extension of the JPEG 2000 standard, which is an image compression standard and coding system. It was created by the Joint Photographic Experts Group committee in 2000 with the intention of superseding the original JPEG standard. JPEG 2000 is known for its high compression efficiency and its ability to handle a wide range of image types, including grayscale, color, and multi-component images. The JPM format specifically extends the capabilities of JPEG 2000 to include support for compound documents, which can contain a mix of text, graphics, and images.
JPM is defined in Part 6 of the JPEG 2000 Suite (ISO/IEC 15444-6), and it is designed to encapsulate multiple images and related data in a single file. This makes it particularly useful for applications such as document imaging, medical imaging, and technical imaging where different types of content need to be stored together. The JPM format allows for the efficient storage of pages within a document, each of which can contain several image regions with different characteristics, as well as non-image data such as annotations or metadata.
One of the key features of JPM is its use of the JPEG 2000 code stream (JPX), which is an extended version of the basic JPEG 2000 code stream (JP2). JPX supports a wider range of color spaces, more sophisticated metadata, and higher bit depths. In a JPM file, each image or 'layer' is stored as a separate JPX code stream. This allows for each layer to be compressed according to its own characteristics, which can lead to more efficient compression and higher quality results, especially for compound documents with diverse content types.
The structure of a JPM file is hierarchical and consists of a series of boxes. A box is a self-contained unit that includes a header and data. The header specifies the type and length of the box, while the data contains the actual content. The top-level box in a JPM file is the signature box, which identifies the file as a JPEG 2000 family file. Following the signature box, there are file type boxes, header boxes, and content boxes, among others. The header boxes contain information about the file, such as the number of pages and the attributes of each page, while the content boxes contain the image data and any associated non-image data.
In terms of compression, JPM files can use both lossless and lossy compression methods. Lossless compression ensures that the original image data can be perfectly reconstructed from the compressed data, which is crucial for applications where image integrity is paramount, such as medical imaging. Lossy compression, on the other hand, allows for smaller file sizes by discarding some of the image data, which can be acceptable in situations where perfect fidelity is not required.
JPM also supports the concept of 'progressive decoding,' which means that a low-resolution version of an image can be displayed while the full-resolution image is still being downloaded or processed. This is particularly useful for large images or slow network connections, as it allows users to get a quick preview without having to wait for the entire file to be available.
Another important aspect of JPM is its support for metadata. Metadata in JPM files can include information about the document, such as the author, title, and keywords, as well as information about each image, such as the capture date, camera settings, and geographic location. This metadata can be stored in XML format, making it easily accessible and modifiable. Additionally, JPM supports the inclusion of ICC profiles, which define the color space of the images, ensuring accurate color reproduction across different devices.
JPM files are also capable of storing multiple versions of an image, each with different resolutions or quality settings. This feature, known as 'multi-layering,' allows for more efficient storage and transmission, as the appropriate version of an image can be selected based on the specific needs of the application or the available bandwidth.
Security is another area where JPM provides robust features. The format supports the inclusion of digital signatures and encryption, which can be used to verify the authenticity of the document and protect sensitive information. This is particularly important in fields like legal and medical document management, where the integrity and confidentiality of the documents are of utmost importance.
Despite its many advantages, the JPM format has not seen widespread adoption, particularly in the consumer market. This is partly due to the complexity of the format and the computational resources required to process JPM files. Additionally, the JPEG 2000 family of standards, including JPM, has been subject to patent licensing issues, which have hindered its adoption compared to the original JPEG standard, which is generally not encumbered by patents.
For software developers and engineers working with JPM files, there are several libraries and tools available that provide support for the format. These include the OpenJPEG library, which is an open-source JPEG 2000 codec, and commercial offerings from various imaging software companies. When working with JPM files, developers must be familiar with the JPEG 2000 code stream syntax, as well as the specific requirements for handling compound documents and metadata.
In conclusion, the JPM image format is a powerful extension of the JPEG 2000 standard that offers a range of features suitable for storing and managing compound documents. Its support for multiple image layers, progressive decoding, metadata, multi-layering, and security features make it an ideal choice for professional and technical applications where image quality and document integrity are critical. While it may not be as commonly used as other image formats, its specialized capabilities ensure that it remains an important tool in fields such as document imaging and medical imaging.
This converter runs entirely in your browser. When you select a file, it is read into memory and converted to the selected format. You can then download the converted file.
Conversions start instantly, and most files are converted in under a second. Larger files may take longer.
Your files are never uploaded to our servers. They are converted in your browser, and the converted file is then downloaded. We never see your files.
We support converting between all image formats, including JPEG, PNG, GIF, WebP, SVG, BMP, TIFF, and more.
This converter is completely free, and will always be free. Because it runs in your browser, we don't have to pay for servers, so we don't need to charge you.
Yes! You can convert as many files as you want at once. Just select multiple files when you add them.