Description
Map a folio side to an image index.
Digital editions connect textual witnesses, anchors, page images and source-specific labels. Literal identifier agreement and numerical offsets preserve a supplied convention without proving textual authority, complete coverage or correct editorial interpretation.
Map a folio side to an image index.
When to use this tool
Use Public Archive Folio Image Offset when checking supplied edition identifiers, ordering or coordinate conventions.
How to use the tool and how it works
- Enter folio, verso, firstFolio, firstRectoImage. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read image. Use the output convention below.
Map a folio side to an image index. Require positive whole folio and firstFolio and nonnegative whole firstRectoImage; image = firstRectoImage+2*(folio-firstFolio)+(verso ? 1 : 0), which must remain nonnegative.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| folio | Folio | Required. Safe integer; minimum 1. |
| verso | Verso | Required. Boolean. |
| firstFolio | First Folio | Required. Safe integer; minimum 1. |
| firstRectoImage | First Recto Image | Required. Safe integer; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| image | Image | Required. Safe integer. |
{
"input": {
"folio": 12,
"verso": true,
"firstFolio": 10,
"firstRectoImage": 5
},
"output": {
"image": 10
}
}Limitations and assumptions
- This assumes exactly two sequential images per folio, without missing leaves or archive lookup.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Inspect the original edition and its encoding model before treating local record agreement as meaningful textual or historical evidence.
References
Similar or alternative tools
- Manuscript Quire Signature Page Offset
Map a uniform quire/leaf position to a page index.
- IIIF Region Normalized Offset
Normalize an in-bounds rectangle to image fractions.