SkPDF: debugging flag - SK_PDF_BASE85_BINARY

If this is defined at compile time, binary date embedded in PDFs are
encoded n base85 to make them more inspectable.  This is only useful to
anyone hacking on SkPDF.

If the flag is unset, there is no change from this CL.

Change-Id: Ib07dc7ef7cedbff17a5fde0ffbeccd24dbeb6a8e
Reviewed-on: https://skia-review.googlesource.com/c/179250
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>

src/pdf/SkPDFBitmap.cpp

@@ -82,7 +82,14 @@ static void emit_dict(SkWStream* stream, SkISize size, const char* colorSpace,
         pdfDict.insertRef("SMask", *smask);
     }
     pdfDict.insertInt("BitsPerComponent", 8);
+    #ifdef SK_PDF_BASE85_BINARY
+    auto filters = SkPDFMakeArray();
+    filters->appendName("ASCII85Decode");
+    filters->appendName("FlateDecode");
+    pdfDict.insertObject("Filter", std::move(filters));
+    #else
     pdfDict.insertName("Filter", "FlateDecode");
+    #endif
     pdfDict.insertInt("Length", length);
     pdfDict.emitObject(stream);
 }
@@ -114,6 +121,10 @@ static SkPDFIndirectReference do_deflated_alpha(const SkPixmap& pm, SkPDFDocumen
         deflateWStream.write(byteBuffer, dst - byteBuffer);
     }
     deflateWStream.finalize();
+
+    #ifdef SK_PDF_BASE85_BINARY
+    SkPDFUtils::Base85Encode(&buffer);
+    #endif
     SkWStream* stream = doc->beginObject(ref);
     emit_dict(stream, pm.info().dimensions(), "DeviceGray", nullptr, buffer.bytesWritten());
     emit_stream(&buffer, stream);
@@ -169,6 +180,9 @@ static void  do_deflated_image(const SkPixmap& pm,
             deflateWStream.write(byteBuffer, dst - byteBuffer);
     }
     deflateWStream.finalize();
+    #ifdef SK_PDF_BASE85_BINARY
+    SkPDFUtils::Base85Encode(&buffer);
+    #endif
     SkWStream* stream = doc->beginObject(ref);
     emit_dict(stream, pm.info().dimensions(), colorSpace,
               sMask.fValue != -1 ? &sMask : nullptr,

src/pdf/SkPDFTypes.cpp

@@ -420,6 +420,8 @@ void SkPDFDict::insertString(const char key[], SkString value) {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+
+
 static void serialize_stream(const SkPDFDict* origDict,
                              SkStreamAsset* stream,
                              bool deflate,
@@ -436,6 +438,17 @@ static void serialize_stream(const SkPDFDict* origDict,
         SkDeflateWStream deflateWStream(&compressedData);
         SkStreamCopy(&deflateWStream, stream);
         deflateWStream.finalize();
+        #ifdef SK_PDF_BASE85_BINARY
+        {
+            SkPDFUtils::Base85Encode(&compressedData);
+            tmp = compressedData.detachAsStream();
+            stream = tmp.get();
+            auto filters = SkPDFMakeArray();
+            filters->appendName("ASCII85Decode");
+            filters->appendName("FlateDecode");
+            dict.insertObject("Filter", std::move(filters));
+        }
+        #else
         if (stream->getLength() > compressedData.bytesWritten() + kMinimumSavings) {
             tmp = compressedData.detachAsStream();
             stream = tmp.get();
@@ -443,6 +456,8 @@ static void serialize_stream(const SkPDFDict* origDict,
         } else {
             SkAssertResult(stream->rewind());
         }
+        #endif
+
     }
     dict.insertInt("Length", stream->getLength());
 

src/pdf/SkPDFTypes.h

@@ -131,6 +131,8 @@ inline void SkPDFArray_Append(SkPDFArray* a, T v, Args... args) {
     SkPDFArray_Append(a, args...);
 }
 
+static inline void SkPDFArray_Append(SkPDFArray* a) {}
+
 template <typename... Args>
 inline sk_sp<SkPDFArray> SkPDFMakeArray(Args... args) {
     auto ret = sk_make_sp<SkPDFArray>();

src/pdf/SkPDFUtils.cpp

@@ -335,3 +335,54 @@ bool SkPDFUtils::ToBitmap(const SkImage* img, SkBitmap* dst) {
     }
     return false;
 }
+
+#ifdef SK_PDF_BASE85_BINARY
+static void base85_fourbytes(uint32_t v, char dst[5]) {
+    for (int n = 4; n > 0; --n) {
+        dst[n] = (v % 85) + '!';
+        v /= 85;
+    }
+    dst[0] = v + '!';
+}
+
+static uint32_t big_end(const uint8_t s[4]) {
+    return ((uint32_t)s[0] << 24) | ((uint32_t)s[1] << 16) | ((uint32_t)s[2] << 8) | s[3];
+}
+
+void SkPDFUtils::Base85Encode(SkDynamicMemoryWStream* dst) {
+    SkASSERT(dst);
+    std::unique_ptr<SkStreamAsset> stream = dst->detachAsStream();
+    SkASSERT(src);
+    size_t remaining = stream->getLength();
+    dst->writeText("\n");
+    int line = 0;
+    while (remaining > 3) {
+        uint8_t src[4];
+        (void)stream->read(src, 4);
+        remaining -= 4;
+        uint32_t v = big_end(src);
+        if (v != 0) {
+            char buffer[5];
+            base85_fourbytes(v, buffer);
+            dst->write(buffer, 5);
+            line += 5;
+        } else {
+            dst->writeText("z");
+            line += 1;
+        }
+        if (line > 74) {
+            dst->writeText("\n");
+            line = 0;
+        }
+    }
+    if (remaining > 0) {
+        SkASSERT(remaining < 4);
+        uint8_t src[4] = {0, 0, 0, 0};
+        (void)stream->read(src, remaining);
+        char buffer[5];
+        base85_fourbytes(big_end(src), buffer);
+        dst->write(buffer, remaining + 1);
+    }
+    dst->writeText("~>\n");
+}
+#endif //  SK_PDF_BASE85_BINARY

src/pdf/SkPDFUtils.h

@@ -125,6 +125,11 @@ void PopulateTilingPatternDict(SkPDFDict* pattern,
                                const SkMatrix& matrix);
 
 bool ToBitmap(const SkImage* img, SkBitmap* dst);
+
+#ifdef SK_PDF_BASE85_BINARY
+void Base85Encode(SkDynamicMemoryWStream*);
+#endif //  SK_PDF_BASE85_BINARY
+
 }  // namespace SkPDFUtils
 
 #endif