Managing JPEG Optimization

Control compression, smoothing, quality, colour quality, copyright text and turn it into a progressive JPEG or a greyscale JPEG at a mouse click.

Here is an image that we want to save as a JPEG. It's been opened in Ignite and a new output file, dune.jpg, has been set up. Of course we could just click the Save this output button on the Inspector and have Ignite automatically save the JPEG with the settings it has chosen. But if we want to take control of the optimization process then we need to look at the JPEG file pane of the Inspector.

Quality: This is the standard quality slider found in every application which compresses JPEGs. Lower quality reduces the quality of the image, and so produces smaller files.

Colour quality: Since brightness and colour are compressed separately in the JPEG file, it is possible to have a different quality setting for brightness and colour. By default, the colour is encoded at the same quality as brightness, but using this slider you can change the colour quality independently.

Smoothing: This applies a degree of smoothing to the image before compressing it. Since JPEG compression works best on images which are composed of smooth changes in colour, this can be very effective in reducing file size. However, it will affect the clarity of images, but a little smoothing may reduce file size and be hardly noticeable, especially at low quality settings.

Vary quality: Standard JPEG compression applies the same quality setting to each 8x8 block in the image. However, in most images, some blocks will have more detail than others, so it's a bit of a waste if the low detail blocks have the same quality as the high detail blocks. When this feature is enabled, Ignite will examine the outputs from stage 3, make a decision on how much quality that block needs, and reduce the quality further if the block is a low quality block. This can lead to quite impressive reductions in file size without affecting quality for some images, such as those with text on a smooth background.

Progressive: 'Yes' saves the image as a progressive JPEG.

Save (c) text: Includes your copyright text in the JPEG file.

Greyscale: Turns your image into a greyscale JPEG which are smaller in file size.

Using settings can streamline your work processes. Find out more next in Using Settings...

contact support@ignite-it.co.uk
copyright © Ben Summers, 1999-2003. All rights reserved