`3. ConversionKey Concepts
rich digital master
proposed method guidelines
BASED ON STROKE WIDTH
Stroke: Adequately rendered cloud outline (left) and inadequately rendered border line (right).
Cornell has developed the following correlation of perceived image quality to pixel coverage:
Quality Index for Stroke Rendering
This formula correlates QI with dpi and stroke width (w) measured in mm. QI in this case is based on the quality assessment above, which correlates to the number of pixels covering the stroke (e.g., 2 = excellent). Note: if the measurement of w is expressed in inches, omit the .039.
For bitonal scanning, the formula is adjusted to compensate for feature drop out in the thresholding process:
Many items falling into this category exhibit features beyond simple edge-based representation, and resolution will not be the sole determinant of image quality. For example, a number of institutions have recommended scanning all manuscripts in grayscale or color.
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