Scanning Guidelines
Palm leaf Manuscripts
Scanning Guidelines
It is recommended that a single scan be done from which all derivatives can be produced.
Benchmarking
The calculations predicted that:
for a bitonal (1 bit) image with a QI = 5, we had to scan at 154 dpi which will lead to 0.13 MB files.
for a greyscale (8 bit) image with a QI = 5, we had to scan at 77 dpi which will lead to 0.3 MB files.
8 bit, 100 dpi, with bicubic interpolation resampling.
There is enough detail to read the manuscript.
8 bit, 300 dpi, , with bicubic interpolation resampling and scaled for comparison with the above image.
It can be noted that we only added unnecessary data.Our Recommendations
If scanning to capture text only,
8-bit, 100 dpi is more than enough to capture the incised text of palm leaf manuscripts. However, at 150 dpi, we can get 1.2 pixels straddling over the finest stroke in the collection, which is expected to give a better image.
The expected file sizes will be 0.45 MB. LZW compression can still reduce this significantly. Recommended file format for master images is TIFF with lossless compression.
If scanning for archival purposes, that is, to capture the artifactual information of the manuscript:
24-bit, 150 dpi which can lead to file sizes of 3 MB.
24-bit, 150 dpi.
There is enough detail to read the text and have an idea of its artifactual value, although we lose structure information. Scanner settings may have to be adjusted to have more contrast.The following are sample images in different file formats.
Full-image of palm-leaf in GIF format. 243KB.
Full-image of palm-leaf in JPG format. 215 KB.
Full-image of palm-leaf in PNG format. 737 KB. Your web browser has to have the PNG plug-in.
Scanner choice
A flatbed-scanner capable of scanning 17 inches would be a good choice for palm leaves. The flexibility of the manuscript may not allow the manuscript to lie flat on the scanner.
It is possible to use an 8" x 11" or 17" scanner for materials longer than 17 inches. But this may not be acceptable in a production environment. Scanning will have to be done in parts at a time. Another scan will have to be made to scan the remaining part. A graphic software can then be used to join the two parts and have a single image that can be scrolled left or right.
A digital camera with a resolution of 3450 x 1050 pixels and 24-bit color would be a good choice for materials up to 23 inches.
Image Enhancement
Image enhancements can be done to the derivatives for better printing and screen display of materials. Brightness and contrast, threshold adjustments can be used for better derivative images.
File format: TIFF
Sticking to a widely accepted file format will make migration later a lot easier.
Compression: LZW (lossless)
LZW is a well-documented file compression algorithm that can be implemented by any decent computer programmer.
Storage Media: CD-ROM
This media does not require additional special handling and storage. Although it has not been proven yet that the information on a CD-ROM can be erased through time, it is a nice idea to check the readability of cd-rom at periodic time intervals.
Having backup copies in different sites increases the chances of recovery.
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