Stirling-PDF/shared-operations/functions/scalePage.ts
2023-11-12 16:57:53 +03:00

56 lines
2.0 KiB
TypeScript

import { PDFPage } from 'pdf-lib';
import { PdfFile, fromPdfLib } from '../wrappers/PdfFile';
export async function scalePage(file: PdfFile, pageSize: {width?:number,height?:number}|{width?:number,height?:number}[]): Promise<PdfFile> {
const pdfDoc = await file.getAsPdfLib();
const pages = pdfDoc.getPages();
if (Array.isArray(pageSize)) {
if (pageSize.length != pages.length) {
throw new Error(`Number of given sizes '${pageSize.length}' is not the same as the number of pages '${pages.length}'`)
}
for (let i=0; i<pageSize.length; i++) {
resize(pages[i], pageSize[i]);
}
} else {
pages.forEach(page => resize(page, pageSize));
}
return fromPdfLib(pdfDoc, file.filename);
};
function resize(page: PDFPage, newSize: {width?:number,height?:number}) {
const calculatedSize = calculateSize(page, newSize);
page.setSize(calculatedSize.width, calculatedSize.height);
const xRatio = calculatedSize.width / page.getWidth();
const yRatio = calculatedSize.height / page.getHeight();
page.scaleContent(xRatio, yRatio);
}
function calculateSize(page: PDFPage, newSize: {width?:number,height?:number}): {width:number,height:number} {
if (!newSize.width && !newSize.height){
throw new Error(`Sizes '${newSize}' cannot have null width and null height`);
} else if (!newSize.width && newSize.height) {
const oldSize = page.getSize();
const ratio = oldSize.width / oldSize.height;
return { width: newSize.height * ratio, height: newSize.height };
} else if (newSize.width && !newSize.height) {
const oldSize = page.getSize();
const ratio = oldSize.height / oldSize.width;
return { width: newSize.width, height: newSize.width * ratio };
}
return { width: newSize.width!, height: newSize.height! };
}
export const PageSize = Object.freeze({
a4: {
width: 594.96,
height: 841.92
},
letter: {
width: 612,
height: 792
}
});