LOW COST, HIGH PERFORMANCE IMAGE VIEWING & ANNOTATION

The Joint Photographic Experts Group (JPEG) image format was the result of work by the Group, which was founded in 1986 to devise a way to deliver photographic quality images to the text terminals used at the time.

JPEG files deliver 24-bit colour images, which means that for each pixel in a digital image, 24 bits of data are allocated to define the exact colour (allowing a possible 16 million colour variations). For large images 24 bits (or 3 bytes) per pixel would general huge file sizes, so JPEGs compress the data using the JPEG compression algorithm.

JPEG files are particularly good at photographic images where there are typically smaller colour variations between neighboring pixels, unlike text or lines on a white sheet where contrasts between neighboring pixels are much greater.

JPEG is generally a 'lossy' compression standard which means some data is inevitably lost during compression (and thus clarity). It is commong for file size to be traded with image quality (smaller files result in lower quality images but quicker download and display speeds, larger files result in higher quality images, but slower download and display speeds).

JPEG compression ratios can be varied according to the pariticular requirements of quality vs file size.

JPEG compression works by allowing pixels of similar colour values to be stored as a single colour block, reducing storage sizes substantially.

Variable JPEG compression allows you to select the degree of compression, so you can pick the point at which the compression begins to affect the viewing of the image. Compression ratios of 20:1 or even 50:1 (for picture based images) without damaging quality loss (for display on a monitor) are generally achievable with JPEGs.

JPEG viewers such as Daeja's ViewONE and ViewONE Pro decompress and render the image data within the JPEG files to the browser screen at high speed, and allow users to perform a range of viewer functions such as zoom in/out, rotate, flip and annotate.

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< link to ViewONE's image viewer pages

< link to ViewONE Pro's image viewer pages