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 JPM images to JNG format. This tool works for both professionals and casual users. Convert your images to JNG in seconds.
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.
JPEG Network Graphics
JPEG compression with PNG transparency.
JNG (JPEG Network Graphics) is a sub-format of the MNG animation format. It was designed to combine the high compression of JPEG with the alpha transparency features of PNG, something that standard JPEG lacks. It essentially wraps a JPEG stream and a mask channel in a chunk-based container.
A JNG file structure mimics PNG. It uses a 8-byte signature and chunks. The image data is split into a color chunk (JDAT) which contains JPEG data, and an alpha chunk (IDAT) which contains PNG-compressed alpha mask. This allows for 'lossy color, lossless alpha' images, which is very space-efficient for photographic sprites.
Created by the PNG Development Group around 2001 as part of the MNG (Multiple-image Network Graphics) project. It failed to gain traction as MNG was rejected by Mozilla and Chromium in favor of APNG and later WebP.
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