User friendly page rotation

[jamie-lemon]

Can we do something in our mupdf.js file to allow for an easy way to rotate a page?

In PyMUPDF we have: https://pymupdf.readthedocs.io/en/latest/the-basics.html#rotating-a-pdf , but I can't see the equivalent in our API.

Please let's add this to the API to match the way PyMuPDF provides it.

[ccxvii]

Here's an example of how to rotate a page with our existing API:

const fs = require("fs")
const mupdf = require("mupdf")

var doc = mupdf.Document.openDocument(fs.readFileSync("input.pdf"), "application/pdf")
var page = doc.loadPage(0)

// Get the PDF object corresponding to the page
var page_obj = page.getObject()

// Look up the existing page rotation (inheritable from the page tree, see PDF reference for details)
var rotate = page_obj.getInheritable("Rotate")
if (!rotate)
    rotate = 0

// Update the Rotate value
page_obj.put("Rotate", rotate + 90)

// Save the changes to a new file.
fs.writeFileSync("output.pdf", doc.saveToBuffer("incremental").asUint8Array())

[jamie-lemon]

I get this - why can't we bundle the 4 lines which do the work into mupdf.js as a method? So I just do e.g. page.rotate(90)

[jamie-lemon]

@ccxvii When I try your code sample I get: TypeError: page.getObject is not a function

[jamie-lemon]

Oh wait - I'm just appreciating the other recent commits - I'll have to package up a local mupdf node package

[jamie-lemon]

@ccxvii Opening this again as in the sample code I think the rotate variable is a pointer and not a rotation value as such.
i.e.

// Look up the existing page rotation (inheritable from the page tree, see PDF reference for details)
    let rotate = page_obj.getInheritable("Rotate")
    console.log("rotate="+rotate) // rotate=11845304
    if (!rotate)
        rotate = 0

    // Update the Rotate value
    page_obj.put("Rotate", rotate + 90)

[jamie-lemon]

Completed, see: https://mupdfjs.readthedocs.io/en/latest/classes/PDFPage.html#rotate