src/pdf/SkPDFUtils.cpp - skia - Git at Google

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */


 #include "SkData.h"
 #include "SkGeometry.h"
 #include "SkPaint.h"
 #include "SkPath.h"
 #include "SkPDFResourceDict.h"
 #include "SkPDFUtils.h"
 #include "SkStream.h"
 #include "SkString.h"
 #include "SkPDFTypes.h"

 #include <cmath>

 sk_sp<SkPDFArray> SkPDFUtils::RectToArray(const SkRect& rect) {
     auto result = sk_make_sp<SkPDFArray>();
     result->reserve(4);
     result->appendScalar(rect.fLeft);
     result->appendScalar(rect.fTop);
     result->appendScalar(rect.fRight);
     result->appendScalar(rect.fBottom);
     return result;
 }

 sk_sp<SkPDFArray> SkPDFUtils::MatrixToArray(const SkMatrix& matrix) {
     SkScalar values[6];
     if (!matrix.asAffine(values)) {
         SkMatrix::SetAffineIdentity(values);
     }

     auto result = sk_make_sp<SkPDFArray>();
     result->reserve(6);
     for (size_t i = 0; i < SK_ARRAY_COUNT(values); i++) {
         result->appendScalar(values[i]);
     }
     return result;
 }

 // static
 void SkPDFUtils::AppendTransform(const SkMatrix& matrix, SkWStream* content) {
     SkScalar values[6];
     if (!matrix.asAffine(values)) {
         SkMatrix::SetAffineIdentity(values);
     }
     for (size_t i = 0; i < SK_ARRAY_COUNT(values); i++) {
         SkPDFUtils::AppendScalar(values[i], content);
         content->writeText(" ");
     }
     content->writeText("cm\n");
 }

 // static
 void SkPDFUtils::MoveTo(SkScalar x, SkScalar y, SkWStream* content) {
     SkPDFUtils::AppendScalar(x, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(y, content);
     content->writeText(" m\n");
 }

 // static
 void SkPDFUtils::AppendLine(SkScalar x, SkScalar y, SkWStream* content) {
     SkPDFUtils::AppendScalar(x, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(y, content);
     content->writeText(" l\n");
 }

 // static
 void SkPDFUtils::AppendCubic(SkScalar ctl1X, SkScalar ctl1Y,
                              SkScalar ctl2X, SkScalar ctl2Y,
                              SkScalar dstX, SkScalar dstY, SkWStream* content) {
     SkString cmd("y\n");
     SkPDFUtils::AppendScalar(ctl1X, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(ctl1Y, content);
     content->writeText(" ");
     if (ctl2X != dstX || ctl2Y != dstY) {
         cmd.set("c\n");
         SkPDFUtils::AppendScalar(ctl2X, content);
         content->writeText(" ");
         SkPDFUtils::AppendScalar(ctl2Y, content);
         content->writeText(" ");
     }
     SkPDFUtils::AppendScalar(dstX, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(dstY, content);
     content->writeText(" ");
     content->writeText(cmd.c_str());
 }

 static void append_quad(const SkPoint quad[], SkWStream* content) {
     SkPoint cubic[4];
     SkConvertQuadToCubic(quad, cubic);
     SkPDFUtils::AppendCubic(cubic[1].fX, cubic[1].fY, cubic[2].fX, cubic[2].fY,
                             cubic[3].fX, cubic[3].fY, content);
 }

 // static
 void SkPDFUtils::AppendRectangle(const SkRect& rect, SkWStream* content) {
     // Skia has 0,0 at top left, pdf at bottom left.  Do the right thing.
     SkScalar bottom = SkMinScalar(rect.fBottom, rect.fTop);

     SkPDFUtils::AppendScalar(rect.fLeft, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(bottom, content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(rect.width(), content);
     content->writeText(" ");
     SkPDFUtils::AppendScalar(rect.height(), content);
     content->writeText(" re\n");
 }

 // static
 void SkPDFUtils::EmitPath(const SkPath& path, SkPaint::Style paintStyle,
                           bool doConsumeDegerates, SkWStream* content) {
     // Filling a path with no area results in a drawing in PDF renderers but
     // Chrome expects to be able to draw some such entities with no visible
     // result, so we detect those cases and discard the drawing for them.
     // Specifically: moveTo(X), lineTo(Y) and moveTo(X), lineTo(X), lineTo(Y).
     enum SkipFillState {
         kEmpty_SkipFillState,
         kSingleLine_SkipFillState,
         kNonSingleLine_SkipFillState,
     };
     SkipFillState fillState = kEmpty_SkipFillState;
     //if (paintStyle != SkPaint::kFill_Style) {
     //    fillState = kNonSingleLine_SkipFillState;
     //}
     SkPoint lastMovePt = SkPoint::Make(0,0);
     SkDynamicMemoryWStream currentSegment;
     SkPoint args[4];
     SkPath::Iter iter(path, false);
     for (SkPath::Verb verb = iter.next(args, doConsumeDegerates);
          verb != SkPath::kDone_Verb;
          verb = iter.next(args, doConsumeDegerates)) {
         // args gets all the points, even the implicit first point.
         switch (verb) {
             case SkPath::kMove_Verb:
                 MoveTo(args[0].fX, args[0].fY, &currentSegment);
                 lastMovePt = args[0];
                 fillState = kEmpty_SkipFillState;
                 break;
             case SkPath::kLine_Verb:
                 AppendLine(args[1].fX, args[1].fY, &currentSegment);
                 if ((fillState == kEmpty_SkipFillState) && (args[0] != lastMovePt)) {
                     fillState = kSingleLine_SkipFillState;
                     break;
                 }
                 fillState = kNonSingleLine_SkipFillState;
                 break;
             case SkPath::kQuad_Verb:
                 append_quad(args, &currentSegment);
                 fillState = kNonSingleLine_SkipFillState;
                 break;
             case SkPath::kConic_Verb: {
                 const SkScalar tol = SK_Scalar1 / 4;
                 SkAutoConicToQuads converter;
                 const SkPoint* quads = converter.computeQuads(args, iter.conicWeight(), tol);
                 for (int i = 0; i < converter.countQuads(); ++i) {
                     append_quad(&quads[i * 2], &currentSegment);
                 }
                 fillState = kNonSingleLine_SkipFillState;
             } break;
             case SkPath::kCubic_Verb:
                 AppendCubic(args[1].fX, args[1].fY, args[2].fX, args[2].fY,
                             args[3].fX, args[3].fY, &currentSegment);
                 fillState = kNonSingleLine_SkipFillState;
                 break;
             case SkPath::kClose_Verb:

                     ClosePath(&currentSegment);

                 currentSegment.writeToStream(content);
                 currentSegment.reset();
                 break;
             default:
                 SkASSERT(false);
                 break;
         }
     }
     if (currentSegment.bytesWritten() > 0) {
         currentSegment.writeToStream(content);
     }
 }

 // static
 void SkPDFUtils::ClosePath(SkWStream* content) {
     content->writeText("h\n");
 }

 // static
 void SkPDFUtils::PaintPath(SkPaint::Style style, SkPath::FillType fill,
                            SkWStream* content) {
     if (style == SkPaint::kFill_Style) {
         content->writeText("f");
     } else if (style == SkPaint::kStrokeAndFill_Style) {
         content->writeText("B");
     } else if (style == SkPaint::kStroke_Style) {
         content->writeText("S");
     }

     if (style != SkPaint::kStroke_Style) {
         NOT_IMPLEMENTED(fill == SkPath::kInverseEvenOdd_FillType, false);
         NOT_IMPLEMENTED(fill == SkPath::kInverseWinding_FillType, false);
         if (fill == SkPath::kEvenOdd_FillType) {
             content->writeText("*");
         }
     }
     content->writeText("\n");
 }

 // static
 void SkPDFUtils::StrokePath(SkWStream* content) {
     SkPDFUtils::PaintPath(
         SkPaint::kStroke_Style, SkPath::kWinding_FillType, content);
 }

 // static
 void SkPDFUtils::DrawFormXObject(int objectIndex, SkWStream* content) {
     content->writeText("/");
     content->writeText(SkPDFResourceDict::getResourceName(
             SkPDFResourceDict::kXObject_ResourceType,
             objectIndex).c_str());
     content->writeText(" Do\n");
 }

 // static
 void SkPDFUtils::ApplyGraphicState(int objectIndex, SkWStream* content) {
     content->writeText("/");
     content->writeText(SkPDFResourceDict::getResourceName(
             SkPDFResourceDict::kExtGState_ResourceType,
             objectIndex).c_str());
     content->writeText(" gs\n");
 }

 // static
 void SkPDFUtils::ApplyPattern(int objectIndex, SkWStream* content) {
     // Select Pattern color space (CS, cs) and set pattern object as current
     // color (SCN, scn)
     SkString resourceName = SkPDFResourceDict::getResourceName(
             SkPDFResourceDict::kPattern_ResourceType,
             objectIndex);
     content->writeText("/Pattern CS/Pattern cs/");
     content->writeText(resourceName.c_str());
     content->writeText(" SCN/");
     content->writeText(resourceName.c_str());
     content->writeText(" scn\n");
 }

 void SkPDFUtils::AppendScalar(SkScalar value, SkWStream* stream) {
     char result[kMaximumFloatDecimalLength];
     size_t len = SkPDFUtils::FloatToDecimal(SkScalarToFloat(value), result);
     SkASSERT(len < kMaximumFloatDecimalLength);
     stream->write(result, len);
 }

 /** Write a string into result, includeing a terminating '\0' (for
     unit testing).  Return strlen(result) (for SkWStream::write) The
     resulting string will be in the form /[-]?([0-9]*.)?[0-9]+/ and
     sscanf(result, "%f", &x) will return the original value iff the
     value is finite. This function accepts all possible input values.

     Motivation: "PDF does not support [numbers] in exponential format
     (such as 6.02e23)."  Otherwise, this function would rely on a
     sprintf-type function from the standard library. */
 size_t SkPDFUtils::FloatToDecimal(float value,
                                   char result[kMaximumFloatDecimalLength]) {
     /* The longest result is -FLT_MIN.
        We serialize it as "-.0000000000000000000000000000000000000117549435"
        which has 48 characters plus a terminating '\0'. */

     /* section C.1 of the PDF1.4 spec (http://goo.gl/0SCswJ) says that
        most PDF rasterizers will use fixed-point scalars that lack the
        dynamic range of floats.  Even if this is the case, I want to
        serialize these (uncommon) very small and very large scalar
        values with enough precision to allow a floating-point
        rasterizer to read them in with perfect accuracy.
        Experimentally, rasterizers such as pdfium do seem to benefit
        from this.  Rasterizers that rely on fixed-point scalars should
        gracefully ignore these values that they can not parse. */
     char* output = &result[0];
     const char* const end = &result[kMaximumFloatDecimalLength - 1];
     // subtract one to leave space for '\0'.

     /* This function is written to accept any possible input value,
        including non-finite values such as INF and NAN.  In that case,
        we ignore value-correctness and and output a syntacticly-valid
        number. */
     if (value == SK_FloatInfinity) {
         value = FLT_MAX;  // nearest finite float.
     }
     if (value == SK_FloatNegativeInfinity) {
         value = -FLT_MAX;  // nearest finite float.
     }
     if (!std::isfinite(value) || value == 0.0f) {
         // NAN is unsupported in PDF.  Always output a valid number.
         // Also catch zero here, as a special case.
         *output++ = '0';
         *output = '\0';
         return output - result;
     }
     // Inspired by:
     // http://www.exploringbinary.com/quick-and-dirty-floating-point-to-decimal-conversion/

     if (value < 0.0) {
         *output++ = '-';
         value = -value;
     }
     SkASSERT(value >= 0.0f);

     // Must use double math to keep precision right.
     double intPart;
     double fracPart = std::modf(static_cast<double>(value), &intPart);
     SkASSERT(intPart + fracPart == static_cast<double>(value));
     size_t significantDigits = 0;
     const size_t maxSignificantDigits = 9;
     // Any fewer significant digits loses precision.  The unit test
     // checks round-trip correctness.
     SkASSERT(intPart >= 0.0 && fracPart >= 0.0);  // negative handled already.
     SkASSERT(intPart > 0.0 || fracPart > 0.0);  // zero already caught.
     if (intPart > 0.0) {
         // put the intPart digits onto a stack for later reversal.
         char reversed[1 + FLT_MAX_10_EXP];  // 39 == 1 + FLT_MAX_10_EXP
         // the largest integer part is FLT_MAX; it has 39 decimal digits.
         size_t reversedIndex = 0;
         do {
             SkASSERT(reversedIndex < sizeof(reversed));
             int digit = static_cast<int>(std::fmod(intPart, 10.0));
             SkASSERT(digit >= 0 && digit <= 9);
             reversed[reversedIndex++] = '0' + digit;
             intPart = std::floor(intPart / 10.0);
         } while (intPart > 0.0);
         significantDigits = reversedIndex;
         SkASSERT(reversedIndex <= sizeof(reversed));
         SkASSERT(output + reversedIndex <= end);
         while (reversedIndex-- > 0) {  // pop from stack, append to result
             *output++ = reversed[reversedIndex];
         }
     }
     if (fracPart > 0 && significantDigits < maxSignificantDigits) {
         *output++ = '.';
         SkASSERT(output <= end);
         do {
             fracPart = std::modf(fracPart * 10.0, &intPart);
             int digit = static_cast<int>(intPart);
             SkASSERT(digit >= 0 && digit <= 9);
             *output++ = '0' + digit;
             SkASSERT(output <= end);
             if (digit > 0 || significantDigits > 0) {
                 // start counting significantDigits after first non-zero digit.
                 ++significantDigits;
             }
         } while (fracPart > 0.0
                  && significantDigits < maxSignificantDigits
                  && output < end);
         // When fracPart == 0, additional digits will be zero.
         // When significantDigits == maxSignificantDigits, we can stop.
         // when output == end, we have filed the string.
         // Note: denormalized numbers will not have the same number of
         // significantDigits, but do not need them to round-trip.
     }
     SkASSERT(output <= end);
     *output = '\0';
     return output - result;
 }

 SkString SkPDFUtils::FormatString(const char* cin, size_t len) {
     SkDEBUGCODE(static const size_t kMaxLen = 65535;)
     SkASSERT(len <= kMaxLen);

     // 7-bit clean is a heuristic to decide what string format to use;
     // a 7-bit clean string should require little escaping.
     bool sevenBitClean = true;
     size_t characterCount = 2 + len;
     for (size_t i = 0; i < len; i++) {
         if (cin[i] > '~' || cin[i] < ' ') {
             sevenBitClean = false;
             break;
         }
         if (cin[i] == '\\' || cin[i] == '(' || cin[i] == ')') {
             ++characterCount;
         }
     }
     SkString result;
     if (sevenBitClean) {
         result.resize(characterCount);
         char* str = result.writable_str();
         *str++ = '(';
         for (size_t i = 0; i < len; i++) {
             if (cin[i] == '\\' || cin[i] == '(' || cin[i] == ')') {
                 *str++ = '\\';
             }
             *str++ = cin[i];
         }
         *str++ = ')';
     } else {
         result.resize(2 * len + 2);
         char* str = result.writable_str();
         *str++ = '<';
         for (size_t i = 0; i < len; i++) {
             uint8_t c = static_cast<uint8_t>(cin[i]);
             static const char gHex[] = "0123456789ABCDEF";
             *str++ = gHex[(c >> 4) & 0xF];
             *str++ = gHex[(c     ) & 0xF];
         }
         *str++ = '>';
     }
     return result;
 }
	/*
	* Copyright 2011 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/


	#include "SkData.h"
	#include "SkGeometry.h"
	#include "SkPaint.h"
	#include "SkPath.h"
	#include "SkPDFResourceDict.h"
	#include "SkPDFUtils.h"
	#include "SkStream.h"
	#include "SkString.h"
	#include "SkPDFTypes.h"

	#include <cmath>

	sk_sp<SkPDFArray> SkPDFUtils::RectToArray(const SkRect& rect) {
	auto result = sk_make_sp<SkPDFArray>();
	result->reserve(4);
	result->appendScalar(rect.fLeft);
	result->appendScalar(rect.fTop);
	result->appendScalar(rect.fRight);
	result->appendScalar(rect.fBottom);
	return result;
	}

	sk_sp<SkPDFArray> SkPDFUtils::MatrixToArray(const SkMatrix& matrix) {
	SkScalar values[6];
	if (!matrix.asAffine(values)) {
	SkMatrix::SetAffineIdentity(values);
	}

	auto result = sk_make_sp<SkPDFArray>();
	result->reserve(6);
	for (size_t i = 0; i < SK_ARRAY_COUNT(values); i++) {
	result->appendScalar(values[i]);
	}
	return result;
	}

	// static
	void SkPDFUtils::AppendTransform(const SkMatrix& matrix, SkWStream* content) {
	SkScalar values[6];
	if (!matrix.asAffine(values)) {
	SkMatrix::SetAffineIdentity(values);
	}
	for (size_t i = 0; i < SK_ARRAY_COUNT(values); i++) {
	SkPDFUtils::AppendScalar(values[i], content);
	content->writeText(" ");
	}
	content->writeText("cm\n");
	}

	// static
	void SkPDFUtils::MoveTo(SkScalar x, SkScalar y, SkWStream* content) {
	SkPDFUtils::AppendScalar(x, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(y, content);
	content->writeText(" m\n");
	}

	// static
	void SkPDFUtils::AppendLine(SkScalar x, SkScalar y, SkWStream* content) {
	SkPDFUtils::AppendScalar(x, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(y, content);
	content->writeText(" l\n");
	}

	// static
	void SkPDFUtils::AppendCubic(SkScalar ctl1X, SkScalar ctl1Y,
	SkScalar ctl2X, SkScalar ctl2Y,
	SkScalar dstX, SkScalar dstY, SkWStream* content) {
	SkString cmd("y\n");
	SkPDFUtils::AppendScalar(ctl1X, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(ctl1Y, content);
	content->writeText(" ");
	if (ctl2X != dstX \|\| ctl2Y != dstY) {
	cmd.set("c\n");
	SkPDFUtils::AppendScalar(ctl2X, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(ctl2Y, content);
	content->writeText(" ");
	}
	SkPDFUtils::AppendScalar(dstX, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(dstY, content);
	content->writeText(" ");
	content->writeText(cmd.c_str());
	}

	static void append_quad(const SkPoint quad[], SkWStream* content) {
	SkPoint cubic[4];
	SkConvertQuadToCubic(quad, cubic);
	SkPDFUtils::AppendCubic(cubic[1].fX, cubic[1].fY, cubic[2].fX, cubic[2].fY,
	cubic[3].fX, cubic[3].fY, content);
	}

	// static
	void SkPDFUtils::AppendRectangle(const SkRect& rect, SkWStream* content) {
	// Skia has 0,0 at top left, pdf at bottom left. Do the right thing.
	SkScalar bottom = SkMinScalar(rect.fBottom, rect.fTop);

	SkPDFUtils::AppendScalar(rect.fLeft, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(bottom, content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(rect.width(), content);
	content->writeText(" ");
	SkPDFUtils::AppendScalar(rect.height(), content);
	content->writeText(" re\n");
	}

	// static
	void SkPDFUtils::EmitPath(const SkPath& path, SkPaint::Style paintStyle,
	bool doConsumeDegerates, SkWStream* content) {
	// Filling a path with no area results in a drawing in PDF renderers but
	// Chrome expects to be able to draw some such entities with no visible
	// result, so we detect those cases and discard the drawing for them.
	// Specifically: moveTo(X), lineTo(Y) and moveTo(X), lineTo(X), lineTo(Y).
	enum SkipFillState {
	kEmpty_SkipFillState,
	kSingleLine_SkipFillState,
	kNonSingleLine_SkipFillState,
	};
	SkipFillState fillState = kEmpty_SkipFillState;
	//if (paintStyle != SkPaint::kFill_Style) {
	// fillState = kNonSingleLine_SkipFillState;
	//}
	SkPoint lastMovePt = SkPoint::Make(0,0);
	SkDynamicMemoryWStream currentSegment;
	SkPoint args[4];
	SkPath::Iter iter(path, false);
	for (SkPath::Verb verb = iter.next(args, doConsumeDegerates);
	verb != SkPath::kDone_Verb;
	verb = iter.next(args, doConsumeDegerates)) {
	// args gets all the points, even the implicit first point.
	switch (verb) {
	case SkPath::kMove_Verb:
	MoveTo(args[0].fX, args[0].fY, &currentSegment);
	lastMovePt = args[0];
	fillState = kEmpty_SkipFillState;
	break;
	case SkPath::kLine_Verb:
	AppendLine(args[1].fX, args[1].fY, &currentSegment);
	if ((fillState == kEmpty_SkipFillState) && (args[0] != lastMovePt)) {
	fillState = kSingleLine_SkipFillState;
	break;
	}
	fillState = kNonSingleLine_SkipFillState;
	break;
	case SkPath::kQuad_Verb:
	append_quad(args, &currentSegment);
	fillState = kNonSingleLine_SkipFillState;
	break;
	case SkPath::kConic_Verb: {
	const SkScalar tol = SK_Scalar1 / 4;
	SkAutoConicToQuads converter;
	const SkPoint* quads = converter.computeQuads(args, iter.conicWeight(), tol);
	for (int i = 0; i < converter.countQuads(); ++i) {
	append_quad(&quads[i * 2], &currentSegment);
	}
	fillState = kNonSingleLine_SkipFillState;
	} break;
	case SkPath::kCubic_Verb:
	AppendCubic(args[1].fX, args[1].fY, args[2].fX, args[2].fY,
	args[3].fX, args[3].fY, &currentSegment);
	fillState = kNonSingleLine_SkipFillState;
	break;
	case SkPath::kClose_Verb:

	ClosePath(&currentSegment);

	currentSegment.writeToStream(content);
	currentSegment.reset();
	break;
	default:
	SkASSERT(false);
	break;
	}
	}
	if (currentSegment.bytesWritten() > 0) {
	currentSegment.writeToStream(content);
	}
	}

	// static
	void SkPDFUtils::ClosePath(SkWStream* content) {
	content->writeText("h\n");
	}

	// static
	void SkPDFUtils::PaintPath(SkPaint::Style style, SkPath::FillType fill,
	SkWStream* content) {
	if (style == SkPaint::kFill_Style) {
	content->writeText("f");
	} else if (style == SkPaint::kStrokeAndFill_Style) {
	content->writeText("B");
	} else if (style == SkPaint::kStroke_Style) {
	content->writeText("S");
	}

	if (style != SkPaint::kStroke_Style) {
	NOT_IMPLEMENTED(fill == SkPath::kInverseEvenOdd_FillType, false);
	NOT_IMPLEMENTED(fill == SkPath::kInverseWinding_FillType, false);
	if (fill == SkPath::kEvenOdd_FillType) {
	content->writeText("*");
	}
	}
	content->writeText("\n");
	}

	// static
	void SkPDFUtils::StrokePath(SkWStream* content) {
	SkPDFUtils::PaintPath(
	SkPaint::kStroke_Style, SkPath::kWinding_FillType, content);
	}

	// static
	void SkPDFUtils::DrawFormXObject(int objectIndex, SkWStream* content) {
	content->writeText("/");
	content->writeText(SkPDFResourceDict::getResourceName(
	SkPDFResourceDict::kXObject_ResourceType,
	objectIndex).c_str());
	content->writeText(" Do\n");
	}

	// static
	void SkPDFUtils::ApplyGraphicState(int objectIndex, SkWStream* content) {
	content->writeText("/");
	content->writeText(SkPDFResourceDict::getResourceName(
	SkPDFResourceDict::kExtGState_ResourceType,
	objectIndex).c_str());
	content->writeText(" gs\n");
	}

	// static
	void SkPDFUtils::ApplyPattern(int objectIndex, SkWStream* content) {
	// Select Pattern color space (CS, cs) and set pattern object as current
	// color (SCN, scn)
	SkString resourceName = SkPDFResourceDict::getResourceName(
	SkPDFResourceDict::kPattern_ResourceType,
	objectIndex);
	content->writeText("/Pattern CS/Pattern cs/");
	content->writeText(resourceName.c_str());
	content->writeText(" SCN/");
	content->writeText(resourceName.c_str());
	content->writeText(" scn\n");
	}

	void SkPDFUtils::AppendScalar(SkScalar value, SkWStream* stream) {
	char result[kMaximumFloatDecimalLength];
	size_t len = SkPDFUtils::FloatToDecimal(SkScalarToFloat(value), result);
	SkASSERT(len < kMaximumFloatDecimalLength);
	stream->write(result, len);
	}

	/** Write a string into result, includeing a terminating '\0' (for
	unit testing). Return strlen(result) (for SkWStream::write) The
	resulting string will be in the form /[-]?([0-9]*.)?[0-9]+/ and
	sscanf(result, "%f", &x) will return the original value iff the
	value is finite. This function accepts all possible input values.

	Motivation: "PDF does not support [numbers] in exponential format
	(such as 6.02e23)." Otherwise, this function would rely on a
	sprintf-type function from the standard library. */
	size_t SkPDFUtils::FloatToDecimal(float value,
	char result[kMaximumFloatDecimalLength]) {
	/* The longest result is -FLT_MIN.
	We serialize it as "-.0000000000000000000000000000000000000117549435"
	which has 48 characters plus a terminating '\0'. */

	/* section C.1 of the PDF1.4 spec (http://goo.gl/0SCswJ) says that
	most PDF rasterizers will use fixed-point scalars that lack the
	dynamic range of floats. Even if this is the case, I want to
	serialize these (uncommon) very small and very large scalar
	values with enough precision to allow a floating-point
	rasterizer to read them in with perfect accuracy.
	Experimentally, rasterizers such as pdfium do seem to benefit
	from this. Rasterizers that rely on fixed-point scalars should
	gracefully ignore these values that they can not parse. */
	char* output = &result[0];
	const char* const end = &result[kMaximumFloatDecimalLength - 1];
	// subtract one to leave space for '\0'.

	/* This function is written to accept any possible input value,
	including non-finite values such as INF and NAN. In that case,
	we ignore value-correctness and and output a syntacticly-valid
	number. */
	if (value == SK_FloatInfinity) {
	value = FLT_MAX; // nearest finite float.
	}
	if (value == SK_FloatNegativeInfinity) {
	value = -FLT_MAX; // nearest finite float.
	}
	if (!std::isfinite(value) \|\| value == 0.0f) {
	// NAN is unsupported in PDF. Always output a valid number.
	// Also catch zero here, as a special case.
	*output++ = '0';
	*output = '\0';
	return output - result;
	}
	// Inspired by:
	// http://www.exploringbinary.com/quick-and-dirty-floating-point-to-decimal-conversion/

	if (value < 0.0) {
	*output++ = '-';
	value = -value;
	}
	SkASSERT(value >= 0.0f);

	// Must use double math to keep precision right.
	double intPart;
	double fracPart = std::modf(static_cast<double>(value), &intPart);
	SkASSERT(intPart + fracPart == static_cast<double>(value));
	size_t significantDigits = 0;
	const size_t maxSignificantDigits = 9;
	// Any fewer significant digits loses precision. The unit test
	// checks round-trip correctness.
	SkASSERT(intPart >= 0.0 && fracPart >= 0.0); // negative handled already.
	SkASSERT(intPart > 0.0 \|\| fracPart > 0.0); // zero already caught.
	if (intPart > 0.0) {
	// put the intPart digits onto a stack for later reversal.
	char reversed[1 + FLT_MAX_10_EXP]; // 39 == 1 + FLT_MAX_10_EXP
	// the largest integer part is FLT_MAX; it has 39 decimal digits.
	size_t reversedIndex = 0;
	do {
	SkASSERT(reversedIndex < sizeof(reversed));
	int digit = static_cast<int>(std::fmod(intPart, 10.0));
	SkASSERT(digit >= 0 && digit <= 9);
	reversed[reversedIndex++] = '0' + digit;
	intPart = std::floor(intPart / 10.0);
	} while (intPart > 0.0);
	significantDigits = reversedIndex;
	SkASSERT(reversedIndex <= sizeof(reversed));
	SkASSERT(output + reversedIndex <= end);
	while (reversedIndex-- > 0) { // pop from stack, append to result
	*output++ = reversed[reversedIndex];
	}
	}
	if (fracPart > 0 && significantDigits < maxSignificantDigits) {
	*output++ = '.';
	SkASSERT(output <= end);
	do {
	fracPart = std::modf(fracPart * 10.0, &intPart);
	int digit = static_cast<int>(intPart);
	SkASSERT(digit >= 0 && digit <= 9);
	*output++ = '0' + digit;
	SkASSERT(output <= end);
	if (digit > 0 \|\| significantDigits > 0) {
	// start counting significantDigits after first non-zero digit.
	++significantDigits;
	}
	} while (fracPart > 0.0
	&& significantDigits < maxSignificantDigits
	&& output < end);
	// When fracPart == 0, additional digits will be zero.
	// When significantDigits == maxSignificantDigits, we can stop.
	// when output == end, we have filed the string.
	// Note: denormalized numbers will not have the same number of
	// significantDigits, but do not need them to round-trip.
	}
	SkASSERT(output <= end);
	*output = '\0';
	return output - result;
	}

	SkString SkPDFUtils::FormatString(const char* cin, size_t len) {
	SkDEBUGCODE(static const size_t kMaxLen = 65535;)
	SkASSERT(len <= kMaxLen);

	// 7-bit clean is a heuristic to decide what string format to use;
	// a 7-bit clean string should require little escaping.
	bool sevenBitClean = true;
	size_t characterCount = 2 + len;
	for (size_t i = 0; i < len; i++) {
	if (cin[i] > '~' \|\| cin[i] < ' ') {
	sevenBitClean = false;
	break;
	}
	if (cin[i] == '\\' \|\| cin[i] == '(' \|\| cin[i] == ')') {
	++characterCount;
	}
	}
	SkString result;
	if (sevenBitClean) {
	result.resize(characterCount);
	char* str = result.writable_str();
	*str++ = '(';
	for (size_t i = 0; i < len; i++) {
	if (cin[i] == '\\' \|\| cin[i] == '(' \|\| cin[i] == ')') {
	*str++ = '\\';
	}
	*str++ = cin[i];
	}
	*str++ = ')';
	} else {
	result.resize(2 * len + 2);
	char* str = result.writable_str();
	*str++ = '<';
	for (size_t i = 0; i < len; i++) {
	uint8_t c = static_cast<uint8_t>(cin[i]);
	static const char gHex[] = "0123456789ABCDEF";
	*str++ = gHex[(c >> 4) & 0xF];
	*str++ = gHex[(c ) & 0xF];
	}
	*str++ = '>';
	}
	return result;
	}