clj-htmltopdf/src/clj_htmltopdf/watermark.clj

(ns clj-htmltopdf.watermark
  (:require
    [clojure.java.io :as io])
  (:import
    [java.io InputStream OutputStream]
    [org.apache.pdfbox.pdmodel PDDocument PDPage PDPageContentStream PDPageContentStream$AppendMode]
    [org.apache.pdfbox.pdmodel.common PDRectangle]
    [org.apache.pdfbox.pdmodel.font PDType1Font PDFont]
    [org.apache.pdfbox.pdmodel.graphics.image PDImageXObject PDImage]
    [org.apache.pdfbox.pdmodel.graphics.state PDExtendedGraphicsState]
    [org.apache.pdfbox.util Matrix]))

; TODO: this is a temporary measure to allow at least _some_ font customizability for watermarks
;       until something more comprehensive can be implemented such as allowing loading of external
;       TTF fonts via PDTrueTypeFont.loadTTF()
(def watermark-fonts
  {"times-roman"           PDType1Font/TIMES_ROMAN
   "times-bold"            PDType1Font/TIMES_BOLD
   "times-italic"          PDType1Font/TIMES_ITALIC
   "times-bolditalic"      PDType1Font/TIMES_BOLD_ITALIC
   "helvetica"             PDType1Font/HELVETICA
   "helvetica-bold"        PDType1Font/HELVETICA_BOLD
   "helvetica-oblique"     PDType1Font/HELVETICA_OBLIQUE
   "helvetica-boldoblique" PDType1Font/HELVETICA_BOLD_OBLIQUE
   "courier"               PDType1Font/COURIER
   "courier-bold"          PDType1Font/COURIER_BOLD
   "courier-oblique"       PDType1Font/COURIER_OBLIQUE
   "courier-boldoblique"   PDType1Font/COURIER_BOLD_OBLIQUE})

(defn render-text-watermark!
  [^PDDocument doc ^PDPage page ^PDPageContentStream cs options]
  (let [font        (or (get watermark-fonts (:font options))
                        (get watermark-fonts "helvetica-bold"))
        font-size   (float (or (:font-size options) 36.0))
        font-color  (or (:color options) [0 0 0])
        text        (:text options)
        text-width  (/ (* (.getStringWidth font text) font-size) 1000.0)
        text-height (/ (* (.getHeight (.getFontBoundingBox (.getFontDescriptor ^PDFont font))) font-size) 1000.0)
        rotation    (float (or (:rotation options) 0))
        page-size   (.getMediaBox page)
        page-width  (.getWidth page-size)
        page-height (.getHeight page-size)
        x           (if (= :center (:x options)) (/ page-width 2) (float (:x options)))
        y           (if (= :center (:y options)) (/ page-height 2) (float (:y options)))
        transform   (doto (Matrix.)
                      (.translate x y)
                      (.rotate (Math/toRadians rotation))
                      (.translate (- (/ text-width 2)) (- (/ text-height 2))))]
    (when (:opacity options)
      (let [r0 (PDExtendedGraphicsState.)]
        (.setNonStrokingAlphaConstant r0 (float (:opacity options)))
        (.setGraphicsStateParameters cs r0)))
    (.beginText cs)
    (.setFont cs font font-size)
    (.setNonStrokingColor cs (int (nth font-color 0)) (int (nth font-color 1)) (int (nth font-color 2)))
    (.setTextMatrix cs transform)
    (.showText cs text)
    (.endText cs)))

(defn render-image-watermark!
  [^PDDocument doc ^PDPage page ^PDPageContentStream cs options]
  (let [image        (PDImageXObject/createFromFileByContent (io/file (:image options)) doc)
        image-width  (.getWidth image)
        image-height (.getHeight image)
        rotation     (float (or (:rotation options) 0))
        page-size    (.getMediaBox page)
        page-width   (.getWidth page-size)
        page-height  (.getHeight page-size)
        x            (if (= :center (:x options)) (/ page-width 2) (float (:x options)))
        y            (if (= :center (:y options)) (/ page-height 2) (float (:y options)))
        transform    (doto (Matrix.)
                       (.translate x y)
                       (.scale (or (:scale-x options) 1.0) (or (:scale-y options) 1.0))
                       (.rotate (Math/toRadians rotation))
                       (.translate (- (/ image-width 2)) (- (/ image-height 2))))]
    (when (:opacity options)
      (let [r0 (PDExtendedGraphicsState.)]
        (.setNonStrokingAlphaConstant r0 (float (:opacity options)))
        (.setGraphicsStateParameters cs r0)))
    (.transform cs transform)
    (.drawImage cs image (float 0) (float 0))))

(defn render-watermark!
  [^PDDocument doc ^PDPage page ^PDPageContentStream cs options]
  (cond
    (:text options)  (render-text-watermark! doc page cs options)
    (:image options) (render-image-watermark! doc page cs options)
    :else            (throw (Exception. "Unknown type of watermark. Either :text or :image should be specified."))))

(defn write-watermark!
  [^InputStream pdf ^OutputStream out {:keys [watermark] :as options}]
  (with-open [doc (PDDocument/load pdf)]
    (doseq [^PDPage page (.getPages doc)]
      (let [cs (PDPageContentStream. doc page PDPageContentStream$AppendMode/APPEND true true)]
        (with-open [cs cs]
          (if (map? watermark)
            (render-watermark! doc page cs watermark)
            (watermark doc page cs)))))
    (.save doc out)
    out))