Dynapik offers a free online tool to change image types - no need to download anything. It's quick and easy to use. You can change your PGM images to JPM format. This tool works for both professionals and casual users. Convert your images to JPM in seconds.
Portable Gray Map
The standard uncompressed grayscale format.
PGM (Portable Gray Map) is the grayscale member of the Netpbm format family. It sits between PBM (1-bit black and white) and PPM (full color). It is designed to store grayscale images where each pixel has a value ranging from black to white, with typical depths of 8-bit (0-255) or 16-bit (0-65535).
Like other Netpbm formats, PGM has two sub-formats: P2 (ASCII) and P5 (Binary). The header defines the dimensions and the maximum gray value (Maxval). In P2, pixel values are written as plain text numbers separated by spaces. In P5, they are raw bytes. It is strictly a single-channel format.
Created by Jef Poskanzer in the late 80s to handle scanned photos that were better than 1-bit bitmaps but didn't need full color. It became a staple in computer vision research and Unix tools.
JPEG 2000 Compound Image
JPEG 2000 for multi-layer documents.
JPM (JPEG 2000 Part 6) is a compound image file format. It is designed for storing document images that contain a mix of text and graphics, using a Mixed Raster Content (MRC) model. It allows for different compression methods to be applied to different 'layers' of the image (e.g., sharp edges for text, smooth gradients for photos).
JPM splits an image into multiple layers (e.g., background, foreground mask, foreground color). Each layer can be compressed differently (e.g., JBIG2 for text mask, JPEG 2000 for background photos), optimizing both quality and file size for scanned documents. This is significantly more efficient than compressing an entire scanned page as a single JPEG 2000 image.
Part of the JPEG 2000 standard (ISO/IEC 15444-6), specifically targeting the document archival market.
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