What is Page Ratio?
The page ratio is the value used to process images to a certain width and height. Image files containing pages are often askew with perspective. It is necessary to physically measure the width and height of the scanned pages to ensure the best dewarp.
When measuring pages, be careful to use the value you will be using for quadrilateral points. For example the Mahan Kosh is approximately 7.5 inches wide from spine to edge of page and almost exactly 11 inches tall. When setting quadrilateral points, often times another quarter inch is being taken off the width. So to calculate the appropriate page ratio we take the width of 7.25 inches and divide by 11 inches to get approximately 0.66 for the page ratio.
Using the preview button in Shabad OS Library will give you an idea of how the page ratio affects the transformation of images. Below you will find some common ratios:
- US Letter (8.5 x 11 inches) will have a width ÷ height ratio of 0.77
- ISO paper sizes are based on the square root of 2 or approximately 0.71
Shabad OS Library basics
- What is Shabad OS Library?
- What is the Page Ratio?
- Workflow
- Interface