SkPDFGradientShader.cpp | Explore in Territory

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/pdf/SkPDFGradientShader.h"

#include "include/core/SkPaint.h"
#include "include/core/SkPathTypes.h"
#include "include/core/SkSpan.h"
#include "include/core/SkStream.h"
#include "include/core/SkTileMode.h"
#include "include/private/base/SkTemplates.h"
#include "include/private/base/SkTo.h"
#include "src/core/SkChecksum.h"
#include "src/core/SkTHash.h"
#include "src/pdf/SkPDFDocumentPriv.h"
#include "src/pdf/SkPDFFormXObject.h"
#include "src/pdf/SkPDFGraphicState.h"
#include "src/pdf/SkPDFResourceDict.h"
#include "src/pdf/SkPDFTypes.h"
#include "src/pdf/SkPDFUtils.h"

#include <cmath>
#include <cstddef>
#include <utility>
#include <vector>

usingnamespaceskia_private;

static uint32_t hash(const SkShaderBase::GradientInfo& v) { … }

static uint32_t hash(const SkPDFGradientShader::Key& k) { … }

static void unit_to_points_matrix(const SkPoint pts[2], SkMatrix* matrix) { … }

static const int kColorComponents = …;
ColorTuple;

/* Assumes t - startOffset is on the stack and does a linear interpolation on t
   between startOffset and endOffset from prevColor to curColor (for each color
   component), leaving the result in component order on the stack. It assumes
   there are always 3 components per color.
   @param range       endOffset - startOffset
   @param beginColor  The previous color.
   @param endColor    The current color.
   @param result      The result ps function.
 */
static void interpolate_color_code(SkScalar range, SkColor beginColor, SkColor endColor,
                                   SkDynamicMemoryWStream* result) { … }

static void write_gradient_ranges(const SkShaderBase::GradientInfo& info, SkSpan<size_t> rangeEnds,
                                  bool top, bool first, SkDynamicMemoryWStream* result) { … }

/* Generate Type 4 function code to map t to the passed gradient, clamping at the ends.
   The types integer, real, and boolean are available.
   There are no string, array, procedure, variable, or name types available.

   The generated code will be of the following form with all values hard coded.

  if (t <= 0) {
    ret = color[0];
    t = 0;
  }
  if (t > 0 && t <= stop[4]) {
    if (t <= stop[2]) {
      if (t <= stop[1]) {
        ret = interp(t - stop[0], stop[1] - stop[0], color[0], color[1]);
      } else {
        ret = interp(t - stop[1], stop[2] - stop[1], color[1], color[2]);
      }
    } else {
      if (t <= stop[3] {
        ret = interp(t - stop[2], stop[3] - stop[2], color[2], color[3]);
      } else {
        ret = interp(t - stop[3], stop[4] - stop[3], color[3], color[4]);
      }
    }
    t = 0;
  }
  if (t > 0) {
    ret = color[4];
  }

   which in PDF will be represented like

  dup 0 le {pop 0 0 0 0} if
  dup dup 0 gt exch 1 le and {
    dup .5 le {
      dup .25 le {
        0 sub 2 mul 0 0
      }{
        .25 sub .5 exch 2 mul 0
      } ifelse
    }{
      dup .75 le {
        .5 sub .5 exch .5 exch 2 mul
      }{
        .75 sub dup 2 mul .5 add exch dup 2 mul .5 add exch 2 mul .5 add
      } ifelse
    } ifelse
  0} if
  0 gt {1 1 1} if
 */
static void gradient_function_code(const SkShaderBase::GradientInfo& info,
                                   SkDynamicMemoryWStream* result) { … }

static std::unique_ptr<SkPDFDict> createInterpolationFunction(const ColorTuple& color1,
                                                    const ColorTuple& color2) { … }

static std::unique_ptr<SkPDFDict> gradientStitchCode(const SkShaderBase::GradientInfo& info) { … }

/* Map a value of t on the stack into [0, 1) for Repeat or Mirror tile mode. */
static void tileModeCode(SkTileMode mode, SkDynamicMemoryWStream* result) { … }

/**
 *  Returns PS function code that applies inverse perspective
 *  to a x, y point.
 *  The function assumes that the stack has at least two elements,
 *  and that the top 2 elements are numeric values.
 *  After executing this code on a PS stack, the last 2 elements are updated
 *  while the rest of the stack is preserved intact.
 *  inversePerspectiveMatrix is the inverse perspective matrix.
 */
static void apply_perspective_to_coordinates(const SkMatrix& inversePerspectiveMatrix,
                                             SkDynamicMemoryWStream* code) { … }

static void linearCode(const SkShaderBase::GradientInfo& info,
                       const SkMatrix& perspectiveRemover,
                       SkDynamicMemoryWStream* function) { … }

static void radialCode(const SkShaderBase::GradientInfo& info,
                       const SkMatrix& perspectiveRemover,
                       SkDynamicMemoryWStream* function) { … }

/* Conical gradient shader, based on the Canvas spec for radial gradients
   See: http://www.w3.org/TR/2dcontext/#dom-context-2d-createradialgradient
 */
static void twoPointConicalCode(const SkShaderBase::GradientInfo& info,
                                const SkMatrix& perspectiveRemover,
                                SkDynamicMemoryWStream* function) { … }

static void sweepCode(const SkShaderBase::GradientInfo& info,
                      const SkMatrix& perspectiveRemover,
                      SkDynamicMemoryWStream* function) { … }


// catch cases where the inner just touches the outer circle
// and make the inner circle just inside the outer one to match raster
static void FixUpRadius(const SkPoint& p1, SkScalar& r1, const SkPoint& p2, SkScalar& r2) { … }

// Finds affine and persp such that in = affine * persp.
// but it returns the inverse of perspective matrix.
static bool split_perspective(const SkMatrix in, SkMatrix* affine,
                              SkMatrix* perspectiveInverse) { … }

static SkPDFIndirectReference make_ps_function(std::unique_ptr<SkStreamAsset> psCode,
                                               std::unique_ptr<SkPDFArray> domain,
                                               std::unique_ptr<SkPDFObject> range,
                                               SkPDFDocument* doc) { … }

static SkPDFIndirectReference make_function_shader(SkPDFDocument* doc,
                                                   const SkPDFGradientShader::Key& state) { … }

static SkPDFIndirectReference find_pdf_shader(SkPDFDocument* doc,
                                              SkPDFGradientShader::Key key,
                                              bool keyHasAlpha);

static std::unique_ptr<SkPDFDict> get_gradient_resource_dict(SkPDFIndirectReference functionShader,
                                                   SkPDFIndirectReference gState) { … }

// Creates a content stream which fills the pattern P0 across bounds.
// @param gsIndex A graphics state resource index to apply, or <0 if no
// graphics state to apply.
static std::unique_ptr<SkStreamAsset> create_pattern_fill_content(int gsIndex,
                                                                  int patternIndex,
                                                                  SkRect& bounds) { … }

static bool gradient_has_alpha(const SkPDFGradientShader::Key& key) { … }

// warning: does not set fHash on new key.  (Both callers need to change fields.)
static SkPDFGradientShader::Key clone_key(const SkPDFGradientShader::Key& k) { … }

static SkPDFIndirectReference create_smask_graphic_state(SkPDFDocument* doc,
                                                     const SkPDFGradientShader::Key& state) { … }

static SkPDFIndirectReference make_alpha_function_shader(SkPDFDocument* doc,
                                                         const SkPDFGradientShader::Key& state) { … }

static SkPDFGradientShader::Key make_key(const SkShader* shader,
                                         const SkMatrix& canvasTransform,
                                         const SkIRect& bbox) { … }

static SkPDFIndirectReference find_pdf_shader(SkPDFDocument* doc,
                                              SkPDFGradientShader::Key key,
                                              bool keyHasAlpha) { … }

SkPDFIndirectReference SkPDFGradientShader::Make(SkPDFDocument* doc,
                                             SkShader* shader,
                                             const SkMatrix& canvasTransform,
                                             const SkIRect& bbox) { … }
chromium/third_party/skia/src/pdf/SkPDFGradientShader.cpp
