@cantoo/pdf-lib
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Create and modify PDF files with JavaScript
112 lines • 5.26 kB
JavaScript
import PDFArray from './objects/PDFArray.js';
import PDFDict from './objects/PDFDict.js';
import PDFName from './objects/PDFName.js';
import PDFRef from './objects/PDFRef.js';
import PDFStream from './objects/PDFStream.js';
import PDFPageLeaf from './structures/PDFPageLeaf.js';
/**
* PDFObjectCopier copies PDFObjects from a src context to a dest context.
* The primary use case for this is to copy pages between PDFs.
*
* _Copying_ an object with a PDFObjectCopier is different from _cloning_ an
* object with its [[PDFObject.clone]] method:
*
* ```
* const src: PDFContext = ...
* const dest: PDFContext = ...
* const originalObject: PDFObject = ...
* const copiedObject = PDFObjectCopier.for(src, dest).copy(originalObject);
* const clonedObject = originalObject.clone();
* ```
*
* Copying an object is equivalent to cloning it and then copying over any other
* objects that it references. Note that only dictionaries, arrays, and streams
* (or structures build from them) can contain indirect references to other
* objects. Copying a PDFObject that is not a dictionary, array, or stream is
* supported, but is equivalent to cloning it.
*/
class PDFObjectCopier {
constructor(src, dest) {
this.traversedObjects = new Map();
// prettier-ignore
this.copy = (object) => (object instanceof PDFPageLeaf ? this.copyPDFPage(object)
: object instanceof PDFDict ? this.copyPDFDict(object)
: object instanceof PDFArray ? this.copyPDFArray(object)
: object instanceof PDFStream ? this.copyPDFStream(object)
: object instanceof PDFRef ? this.copyPDFIndirectObject(object)
: object.clone());
this.copyPDFPage = (originalPage) => {
const clonedPage = originalPage.clone();
// Move any entries that the originalPage is inheriting from its parent
// tree nodes directly into originalPage so they are preserved during
// the copy.
const { InheritableEntries } = PDFPageLeaf;
for (let idx = 0, len = InheritableEntries.length; idx < len; idx++) {
const key = PDFName.of(InheritableEntries[idx]);
const value = clonedPage.getInheritableAttribute(key);
if (!clonedPage.get(key) && value)
clonedPage.set(key, value);
}
// Remove the parent reference to prevent the whole donor document's page
// tree from being copied when we only need a single page.
clonedPage.delete(PDFName.of('Parent'));
return this.copyPDFDict(clonedPage);
};
this.copyPDFDict = (originalDict) => {
if (this.traversedObjects.has(originalDict)) {
return this.traversedObjects.get(originalDict);
}
const clonedDict = originalDict.clone(this.dest);
this.traversedObjects.set(originalDict, clonedDict);
const entries = originalDict.entries();
for (let idx = 0, len = entries.length; idx < len; idx++) {
const [key, value] = entries[idx];
clonedDict.set(key, this.copy(value));
}
return clonedDict;
};
this.copyPDFArray = (originalArray) => {
if (this.traversedObjects.has(originalArray)) {
return this.traversedObjects.get(originalArray);
}
const clonedArray = originalArray.clone(this.dest);
this.traversedObjects.set(originalArray, clonedArray);
for (let idx = 0, len = originalArray.size(); idx < len; idx++) {
const value = originalArray.get(idx);
clonedArray.set(idx, this.copy(value));
}
return clonedArray;
};
this.copyPDFStream = (originalStream) => {
if (this.traversedObjects.has(originalStream)) {
return this.traversedObjects.get(originalStream);
}
const clonedStream = originalStream.clone(this.dest);
this.traversedObjects.set(originalStream, clonedStream);
const entries = originalStream.dict.entries();
for (let idx = 0, len = entries.length; idx < len; idx++) {
const [key, value] = entries[idx];
clonedStream.dict.set(key, this.copy(value));
}
return clonedStream;
};
this.copyPDFIndirectObject = (ref) => {
const alreadyMapped = this.traversedObjects.has(ref);
if (!alreadyMapped) {
const newRef = this.dest.nextRef();
this.traversedObjects.set(ref, newRef);
const dereferencedValue = this.src.lookup(ref);
if (dereferencedValue) {
const cloned = this.copy(dereferencedValue);
this.dest.assign(newRef, cloned);
}
}
return this.traversedObjects.get(ref);
};
this.src = src;
this.dest = dest;
}
}
PDFObjectCopier.for = (src, dest) => new PDFObjectCopier(src, dest);
export default PDFObjectCopier;
//# sourceMappingURL=PDFObjectCopier.js.map