David Green
posted this on November 28, 2011 06:14 pm
This article provides more information on two related topics:
Shozam always processes images that it generates. You can control the file size vs. compression trade-offs in Step 5 on the Image tab for all images or in Step 2 on the Other tab on an image by image basis. Setting the slider all the way to 100 means that the program will minimize the compression of the file; the JPEG compression algorithm will provide utmost fidelity to the "original" image given. This works the same as in Adobe Photoshop when you maximize the quality of the JPEG compression (and probably the same as in your image editing program). JPEG image processing/compression has to happen each time the image is saved.Setting the slider to 100 does not mean the image will not get processed/compressed; it just means that it will compress it very little in order to achieve highest fidelity, albeit at a much larger size.
It is important to realize that if the image was already compressed for a certain file size vs. quality ratio, then setting the JPEG quality slider to 100 will only increase file size with no increase of quality. The quality of the image cannot be increased beyond that of the original, particularly if no scaling is being performed on the image.
Preventing processing of images is not typically possible at this point with Shozam but may be a feature we can consider adding at a later time (give option to not process any images that do not need to be scaled). Note that if the original image fits the size of the Large Pages but it is larger than images to fit the QuickView Pages, the images would still need to be "touched" to be scaled down for the QuickView Pages and thus processed including using the Shozam engine to do JPEG compression. So the benefit of a feature to leave "large" images alone will be limited to the Large Page images.
There are two cases by which images bypass the Shozam image processing engine: