PDF image extraction in Swift

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

import PDFNet
import Foundation

//-----------------------------------------------------------------------------------
// This sample illustrates one approach to PDF image extraction
// using PDFNet.
//
// Note: Besides direct image export, you can also convert PDF images
// to GDI+ Bitmap, or extract uncompressed/compressed image data directly
// using element.GetImageData() (e.g. as illustrated in ElementReaderAdv
// sample project).
//-----------------------------------------------------------------------------------

var image_counter: Int = 0

func ImageExtract(reader: PTElementReader) {
    while let element = reader.next() {
        switch element.getType() {
        case e_ptimage, e_ptinline_image:
            image_counter += 1
            print("--> Image: \(image_counter)")
            print("    Width: \(element.getImageWidth())")
            print("    Height: \(element.getImageHeight())")
            print("    BPC: \(element.getBitsPerComponent())")
            
            let ctm: PTMatrix2D = element.getCTM()
            let x2: Double = 1
            let y2: Double = 1
            ctm.mult(PTPDFPoint(px: x2, py: y2))
            print("    Coords: x1=\(ctm.getM_h()), y1=\(ctm.getM_v()), x2=\(x2), y2=\(y2)")
            
            if element.getType() == e_ptimage {
                let image: PTImage = PTImage(image_xobject: element.getXObject())
                let path: String = URL(fileURLWithPath: URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("").absoluteString).appendingPathComponent("image_extract1_\(image_counter)").path
                image.export(toFile: path)
            }
        case e_ptform:
            // Process form XObjects
            reader.formBegin()
            ImageExtract(reader: reader)
            reader.end()
        default:
            break
        }
    }
}

func runImageExtractTest() -> Int {
    return autoreleasepool {
        var ret: Int = 0
        
        // Initialize PDFNet
        
        
        // Example 1:
        // Extract images by traversing the display list for
        // every page. With this approach it is possible to obtain
        // image positioning information and DPI.
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "newsletter", ofType: "pdf"))
                doc.initSecurityHandler()
                
                let reader: PTElementReader = PTElementReader()
                //  Read every page
                let itr: PTPageIterator = doc.getPageIterator(1)
                while itr.hasNext() {
                    reader.begin(itr.current())
                    ImageExtract(reader: reader)
                    reader.end()
                    itr.next()
                }
                
                print("Done...")
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        print("----------------------------------------------------------------")
        
        // Example 2:
        // Extract images by scanning the low-level document.
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "newsletter", ofType: "pdf"))
                doc.initSecurityHandler()
                
                image_counter = 0
                
                let cos_doc: PTSDFDoc = doc.getSDFDoc()
                let num_objs = cos_doc.xRefSize()
                for i in 1..<num_objs {
                    guard let obj: PTObj = cos_doc.getObj(i) else {
                        continue
                    }
                    if !obj.isFree() && obj.isStream() {
                        // Process only images
                        var itr: PTDictIterator = obj.find("Type")
                        if !itr.hasNext() || !(itr.value().getName() == "XObject") {
                            continue
                        }
                        
                        itr = obj.find("Subtype")
                        if !itr.hasNext() || !(itr.value().getName() == "Image") {
                            continue
                        }
                        
                        let image: PTImage = PTImage(image_xobject: obj)
                        image_counter += 1
                        print("-. Image: \(image_counter)")
                        print("    Width: \(image.getWidth())")
                        print("    Height: \(image.getHeight())")
                        print("    BPC: \(image.getBitsPerComponent())")
                        
                        let path: String = URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("image_extract2_\(image_counter)").path
                        image.export(toFile: path)
                    }
                }
                
                print("Done...")
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        return ret
    }
}