High quality UIImage from PDF

Question

I\'m converting a PDF page into a UIImage. While doing so, I lose the image quality. Need help in getting high quality images.

Code to generate UIImage

Answer 1

This one gives the best quality... if you need another quality just change dpi.

    func drawPDFfromURL(url: URL) -> UIImage? {
    guard let document = CGPDFDocument(url as CFURL) else { return nil }
    guard let page = document.page(at: 1) else { return nil }
    let dpi: CGFloat = 300.0 / 72.0
    let pageRect = page.getBoxRect(.mediaBox)

    let renderer = UIGraphicsImageRenderer(size: CGSize(width: pageRect.size.width * dpi, height: pageRect.size.height * dpi))

    let img1 = renderer.jpegData(withCompressionQuality: 1.0, actions: { cnv in
          UIColor.white.set()
          cnv.fill(pageRect)
          cnv.cgContext.translateBy(x: 0.0, y: pageRect.size.height * dpi);
          cnv.cgContext.scaleBy(x: dpi, y: -dpi);
          cnv.cgContext.drawPDFPage(page);

        })
    let img2 = UIImage(data: img1)
    return img2
}

Answer 2

When you ask the PDF for it's page size, you're getting a width/height for 72 PPI. You might try creating a context that's scaled up using a scale transform. For example, if you wanted to render at 300 dpi, add a scale transform to scale by 300.0/72.0.

If you export as TIFF, you will be able to encapsulate the final PPI (300) of the generated image.

Answer 3

I've written a handy UIImage PDF renderer category that you may find helpful. It also caches all rendered results for high performance.

https://github.com/mindbrix/UIImage-PDF

Answer 4

As of iOS 11.0, macOS 10.13, Mac Catalyst 13.0 you can use thumbnailOfSize:forBox:

Answer 5

Try this code for Swift 3 :

func drawPDFfromURL(url: URL) -> UIImage? {
    guard let document = CGPDFDocument(url as CFURL) else { return nil }
    guard let page = document.page(at: 1) else { return nil }

    let pageRect = page.getBoxRect(.mediaBox)
    let renderer = UIGraphicsImageRenderer(size: pageRect.size)
    let img1 = renderer.jpegData(withCompressionQuality: 1.0, actions: { cnv in
        UIColor.white.set()
        cnv.fill(pageRect)
        cnv.cgContext.translateBy(x: 0.0, y: pageRect.size.height);
        cnv.cgContext.scaleBy(x: 1.0, y: -1.0);
        cnv.cgContext.drawPDFPage(page);
    })
    let img2 = UIImage(data: img1)
    return img2
}

This gives much higher resolution

Answer 6

import PDFKit

let pdfDocument = PDFDocument(url: pdfUrl)!
let thumb = pdfDocument.page(at: pageIndex)?.thumbnail(of: size, for: .mediaBox)