PSOutputDev: use the DeviceN8 bitmap for rasterization with CMYK-output + overprint

This mostly mimics the pdftoppm behaviour.

3 files changed, 153 insertions, 5 deletions

diff --git a/poppler/PSOutputDev.cc b/poppler/PSOutputDev.cc
index 67ae28fe..e77d0ed6 100644
--- a/poppler/PSOutputDev.cc
+++ b/poppler/PSOutputDev.cc
@@ -3141,6 +3141,7 @@ bool PSOutputDev::checkPageSlice(Page *page, double /*hDPI*/, double /*vDPI*/, i
     unsigned char digit;
     bool isOptimizedGray;
     bool overprint;
+    SplashColorMode internalColorFormat;
 #endif
 
     if (!postInitDone) {
@@ -3176,13 +3177,25 @@ bool PSOutputDev::checkPageSlice(Page *page, double /*hDPI*/, double /*vDPI*/, i
     startPage(page->getNum(), state, xref);
     delete state;
 
+    // If we would not rasterize this page, we would emit the overprint code anyway for language level 2 and upwards.
+    // As such it is safe to assume for a CMYK printer that it would respect the overprint operands.
+    overprint = globalParams->getOverprintPreview() || (processColorFormat == splashModeCMYK8 && level >= psLevel2);
+
     // set up the SplashOutputDev
+    internalColorFormat = processColorFormat;
     if (processColorFormat == splashModeMono8) {
         numComps = 1;
         paperColor[0] = 0xff;
     } else if (processColorFormat == splashModeCMYK8) {
         numComps = 4;
         paperColor[0] = paperColor[1] = paperColor[2] = paperColor[3] = 0;
+
+        // If overprinting is emulated, it is not sufficient to just store the CMYK values in a bitmap.
+        // All separation channels need to be stored and collapsed at the end.
+        // Cf. PDF32000_2008 Section 11.7.4.5 and Tables 148, 149
+        if (overprint) {
+            internalColorFormat = splashModeDeviceN8;
+        }
     } else if (processColorFormat == splashModeRGB8) {
         numComps = 3;
         paperColor[0] = paperColor[1] = paperColor[2] = 0xff;
@@ -3192,10 +3205,7 @@ bool PSOutputDev::checkPageSlice(Page *page, double /*hDPI*/, double /*vDPI*/, i
         numComps = 3;
         paperColor[0] = paperColor[1] = paperColor[2] = 0xff;
     }
-    // If we would not rasterize this page, we would emit the overprint code anyway for language level 2 and upwards.
-    // As such it is safe to assume for a CMYK printer that it would respect the overprint operands.
-    overprint = globalParams->getOverprintPreview() || (processColorFormat == splashModeCMYK8 && level >= psLevel2);
-    splashOut = new SplashOutputDev(processColorFormat, 1, false, paperColor, false, splashThinLineDefault, overprint);
+    splashOut = new SplashOutputDev(internalColorFormat, 1, false, paperColor, false, splashThinLineDefault, overprint);
     splashOut->setFontAntialias(rasterAntialias);
     splashOut->setVectorAntialias(rasterAntialias);
 #    ifdef USE_CMS
@@ -3440,7 +3450,11 @@ bool PSOutputDev::checkPageSlice(Page *page, double /*hDPI*/, double /*vDPI*/, i
         case psLevel3:
         case psLevel3Sep:
             p = bitmap->getDataPtr() + (h - 1) * bitmap->getRowSize();
-            str0 = new MemStream((char *)p, 0, w * h * numComps, Object(objNull));
+            if (processColorFormat == splashModeCMYK8 && internalColorFormat != splashModeCMYK8) {
+                str0 = new SplashBitmapCMYKEncoder(bitmap);
+            } else {
+                str0 = new MemStream((char *)p, 0, w * h * numComps, Object(objNull));
+            }
             // Check for a color image that uses only gray
             if (!getOptimizeColorSpace()) {
                 isOptimizedGray = false;
diff --git a/poppler/Stream.cc b/poppler/Stream.cc
index 4971e2ed..ab850a91 100644
--- a/poppler/Stream.cc
+++ b/poppler/Stream.cc
@@ -68,6 +68,10 @@
 #include "Stream-CCITT.h"
 #include "CachedFile.h"
 
+#ifdef HAVE_SPLASH
+#    include "splash/SplashBitmap.h"
+#endif
+
 #ifdef ENABLE_LIBJPEG
 #    include "DCTStream.h"
 #endif
@@ -5137,3 +5141,81 @@ bool RGBGrayEncoder::fillBuf()
     *bufEnd++ = (char)i;
     return true;
 }
+
+//------------------------------------------------------------------------
+// SplashBitmapCMYKEncoder
+//------------------------------------------------------------------------
+
+#ifdef HAVE_SPLASH
+SplashBitmapCMYKEncoder::SplashBitmapCMYKEncoder(SplashBitmap *bitmapA) : bitmap(bitmapA)
+{
+    width = (size_t)4 * bitmap->getWidth();
+    height = bitmap->getHeight();
+    buf.resize(width);
+    bufPtr = width;
+    curLine = height - 1;
+}
+
+SplashBitmapCMYKEncoder::~SplashBitmapCMYKEncoder() { }
+
+void SplashBitmapCMYKEncoder::reset()
+{
+    bufPtr = width;
+    curLine = height - 1;
+}
+
+int SplashBitmapCMYKEncoder::lookChar()
+{
+    if (bufPtr >= width && !fillBuf()) {
+        return EOF;
+    }
+    return buf[bufPtr];
+}
+
+int SplashBitmapCMYKEncoder::getChar()
+{
+    int ret = lookChar();
+    bufPtr++;
+    return ret;
+}
+
+bool SplashBitmapCMYKEncoder::fillBuf()
+{
+    if (curLine < 0) {
+        return false;
+    }
+
+    if (bufPtr < width) {
+        return true;
+    }
+
+    bitmap->getCMYKLine(curLine, &buf[0]);
+    bufPtr = 0;
+    curLine--;
+    return true;
+}
+
+Goffset SplashBitmapCMYKEncoder::getPos()
+{
+    return (height - 1 - curLine) * width + bufPtr;
+}
+
+void SplashBitmapCMYKEncoder::setPos(Goffset pos, int dir)
+{
+    // This code is mostly untested!
+    if (dir < 0) {
+        curLine = pos / width;
+    } else {
+        curLine = height - 1 - pos / width;
+    }
+
+    bufPtr = width;
+    fillBuf();
+
+    if (dir < 0) {
+        bufPtr = width - 1 - pos % width;
+    } else {
+        bufPtr = pos % width;
+    }
+}
+#endif
diff --git a/poppler/Stream.h b/poppler/Stream.h
index c6b363f6..720811ba 100644
--- a/poppler/Stream.h
+++ b/poppler/Stream.h
@@ -47,6 +47,9 @@
 class GooFile;
 class BaseStream;
 class CachedFile;
+#ifdef HAVE_SPLASH
+class SplashBitmap;
+#endif
 
 //------------------------------------------------------------------------
 
@@ -1428,4 +1431,53 @@ private:
     bool fillBuf();
 };
 
+//------------------------------------------------------------------------
+// SplashBitmapCMYKEncoder
+//
+// This stream helps to condense SplashBitmaps (mostly of DeviceN8 type) into
+// pure CMYK colors. In particular for a DeviceN8 bitmap it redacts the spot colorants.
+//------------------------------------------------------------------------
+
+#ifdef HAVE_SPLASH
+class SplashBitmapCMYKEncoder : public Stream
+{
+public:
+    SplashBitmapCMYKEncoder(SplashBitmap *bitmapA);
+    ~SplashBitmapCMYKEncoder() override;
+    StreamKind getKind() const override { return strWeird; }
+    void reset() override;
+    int getChar() override;
+    int lookChar() override;
+    GooString *getPSFilter(int /*psLevel*/, const char * /*indent*/) override { return nullptr; }
+    bool isBinary(bool /*last = true*/) override { return true; }
+
+    // Although we are an encoder, we return false here, since we do not want do be auto-deleted by
+    // successive streams.
+    bool isEncoder() override { return false; }
+
+    int getUnfilteredChar() override { return getChar(); }
+    void unfilteredReset() override { reset(); }
+
+    BaseStream *getBaseStream() override { return nullptr; }
+    Stream *getUndecodedStream() override { return this; }
+
+    Dict *getDict() override { return nullptr; }
+    Object *getDictObject() override { return nullptr; }
+
+    Goffset getPos() override;
+    void setPos(Goffset pos, int dir = 0) override;
+
+private:
+    SplashBitmap *bitmap;
+    size_t width;
+    int height;
+
+    std::vector<unsigned char> buf;
+    size_t bufPtr;
+    int curLine;
+
+    bool fillBuf();
+};
+#endif
+
 #endif