Foxit pdf SDK for IOS

    /** @brief	Render a specified page to Bitmap, and save it to a PNG image. */
    func renderPage(_ page: FSPDFPage, atPath path: String) -> Bool {
        if path == "" {
            return false
        }
        if !page.isParsed() {
            if !PlatformAPIDemo.parsePage(page, reparse: true) {
                return false
            }
        }
        //create bitmap
        let pageWidth: Int = Int(page.getWidth())
        let pageHeight: Int = Int(page.getHeight())
        
        let bmp = FSBitmap(width: Int32(pageWidth), height: Int32(pageHeight), format: .dibRgb32, buffer: nil, pitch: 0)!
        
        bmp.fillRect(0xffffffff, rect: nil)
        //init renderer
        let render = FSRenderer.init(bitmap: bmp, is_rgb_order: true) 
        if render == nil {
            return false
        }
        
        //set different kinds of properties
        render!.setRenderContentFlags(1)
        render!.setTransformAnnotIcon(true)
        render!.setColorMode(FSRendererColorMode.normal)
        render!.setMappingModeColors(0xffffffff, foreground_color: 0x0000ffff)
        render!.setForceHalftone(true)
        let mat = page.getDisplayMatrix(0, top: 0, width: Int32(pageWidth), height: Int32(pageHeight), rotate: .rotation0)
        let progressive = render!.startRender(page, matrix: mat, pause: nil)
        if progressive != nil {
            while true {
                let state = progressive!.resume()
                if state == .error {
                    return false
                } else if state != .toBeContinued {
                    break;
                }
            }
        }
        if !self.save2PNGWithBitmap(bmp, transform: nil, Path: path as NSString) {
            return false
        }
        return true
    } 
	
    func save2PNGWithBitmap(_ fsBitmap: FSBitmap, transform: CGAffineTransform?, Path path: NSString) -> Bool {
        if path == "" {
            return false
        }
        let pageWidth: Int = Int(fsBitmap.getWidth())
        let pageHeight: Int = Int(fsBitmap.getHeight())
        if pageWidth <= 0 || pageHeight <= 0 {
            return false
        }

        let provider = CGDataProvider.init(data: fsBitmap.getBuffer() as CFData)
        
        let image = CGImage(width: pageWidth, height: pageHeight, bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: Int(fsBitmap.getPitch()), space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: .byteOrder32Big, provider: provider!, decode: nil, shouldInterpolate: true, intent: .defaultIntent)!
        let uiImage = UIImage(cgImage: image)
        let fileURL = URL(fileURLWithPath: path as String)
        do {
            try UIImagePNGRepresentation(uiImage)!.write(to: fileURL)
        } catch {
            print(error)
            return false
        }
        return true
    }