Quote:
Originally Posted by Hitch
You calculate the image size you need based on the device, if you are making a book strictly for one device. If you're not, you're guesstimating, and at that point, you say, well, the average reading device is ~3.5" wide, and thus, this image will be somewhere between X and Y, X being (for example, 75ppi) one figure for width and Y being the greater if you're thinking 96 or higher. No?
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IMHO, no.
I think an overview of the optimum process is this:
1. Scan at the native rez of the scanner. The idea here is that it is better to resample in another program that gives you more control over the process than using the scanner software.
2. Use an image processing program to crop and resample the image to the desired final size (in pixels). (More below on "desired final size")
3. Save in a format (GIF, PNG, JPEG
, SVG) optimum for quality v. size tradeoff for that image and intended display devices.
On color and bits per pixel: if your target is current e-readers using electronic paper displays, then only 4-bit grayscale is needed, since they only support 16 levels of gray. Or if the source image is monochrome, there is no reason to use anything that takes more file space than 8-bit grayscale.
On image size: the target for resizing for optimum quality (without zoom in the reader) is the minimum available width and height for images across the target displays. This may not be the physical width and height in pixels, but something less. For example, if the two target devices both have physical 600wx800h displays, and one has an available display area of 590x780, and the other has a display area of 580wx790h, then the image should be resized to 580x780. This is to avoid resizing in any of the readers' software.