Overview
The goal of image file size optimization is to reduce the size of image files without losing significant quality. Reducing the size of image files reduces the size of your book.
This help pages describes manual image file size optimization. Gedcom Publisher includes the Exhibits.Optimize Image Files property to enable automated image file size optimization. Gedcom Publisher's automated tool will do a reasonable job, but manual optimization provides the opportunity to fine-tune the changes to the specific content of the image.
Save the Original
Never alter the original image file. Make a copy and edit the copy. Save the original in a safe place. Use the optimized image with Gedcom Publisher.
If you want to use the optimized image with your genealogy application and with Gedcom Publisher, adjust the image's file path in your genealogy application to refer to the optimized image file rather than the original image file.
If you want to use the original image with your genealogy application, but you want to use an optimized image with Gedcom Publisher, see the instructions for using the Exhibits.Alternate Folder property .
Steps
These are the basic steps in image file size optimization.
- Avoid uncompressed image types, like TIF. Convert those images to JPG or PNG.
Typically, you should choose JPG for photographs and PNG for scanned documents. PNG is better for documents because it often will render small text, lines, and other man-made graphics more precisely than JPG. However, if JPG yields a legible version of a scanned document, and the JPG image file is smaller than a PNG version, use the JPG version.
- Reduce the pixel dimensions of large images.
For example, if an image is 3000 pixels by 2000 pixels, reduce it to 1500 pixels by 1000 pixels, or smaller. Reducing the pixel-dimensions of an image will significantly reduce the size of the image file.
Many people reading your book will be using devices with small screens. The E-book reader will reduce the pixel dimensions to fit the device window, so using a large image increases the file size of your book without increasing image quality.
- For PNG images, reduce the size of the color palette.
A PNG image using 64 colors will have a smaller image file than a PNG image using 256 colors.
This optimization has to be applied carefully; reducing the size of the color palette may degrade the image to an unacceptable level.
- For JPG images, increase the compression level.
Use the highest compression that yields a good quality image. You may be surprised that high compression levels (AKA "low quality") often yield acceptable images.
When saving a JPG/JPEG image, some image editors refer to image quality rather than compression level. Image quality and compression level have an inverse relationship: high image quality means low compression level, and low image quality means high compression level.