ui/gfx/canvas.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ui/gfx/canvas.h"
   6
   7 #include <cmath>
   8 #include <limits>
   9
  10 #include "base/i18n/rtl.h"
  11 #include "base/logging.h"
  12 #include "third_party/skia/include/core/SkBitmap.h"
  13 #include "third_party/skia/include/effects/SkGradientShader.h"
  14 #include "ui/gfx/font_list.h"
  15 #include "ui/gfx/rect.h"
  16 #include "ui/gfx/size_conversions.h"
  17 #include "ui/gfx/skia_util.h"
  18 #include "ui/gfx/transform.h"
  19
  20 #if defined(OS_WIN)
  21 #include "ui/gfx/canvas_skia_paint.h"
  22 #endif
  23
  24 namespace gfx {
  25
  26 Canvas::Canvas(const Size& size, float image_scale, bool is_opaque)
  27     : image_scale_(image_scale),
  28       canvas_(NULL) {
  29   Size pixel_size = ToCeiledSize(ScaleSize(size, image_scale));
  30   owned_canvas_ = skia::AdoptRef(skia::CreatePlatformCanvas(pixel_size.width(),
  31                                                             pixel_size.height(),
  32                                                             is_opaque));
  33   canvas_ = owned_canvas_.get();
  34 #if defined(OS_WIN) || defined(OS_MACOSX)
  35   // skia::PlatformCanvas instances are initialized to 0 by Cairo on Linux, but
  36   // uninitialized on Win and Mac.
  37   if (!is_opaque)
  38     owned_canvas_->clear(SkColorSetARGB(0, 0, 0, 0));
  39 #endif
  40
  41   SkScalar scale_scalar = SkFloatToScalar(image_scale);
  42   canvas_->scale(scale_scalar, scale_scalar);
  43 }
  44
  45 Canvas::Canvas(const ImageSkiaRep& image_rep, bool is_opaque)
  46     : image_scale_(image_rep.scale()),
  47       owned_canvas_(skia::AdoptRef(
  48           skia::CreatePlatformCanvas(image_rep.pixel_width(),
  49                                      image_rep.pixel_height(),
  50                                      is_opaque))),
  51       canvas_(owned_canvas_.get()) {
  52   SkScalar scale_scalar = SkFloatToScalar(image_scale_);
  53   canvas_->scale(scale_scalar, scale_scalar);
  54   DrawImageInt(ImageSkia(image_rep), 0, 0);
  55 }
  56
  57 Canvas::Canvas()
  58     : image_scale_(1.0),
  59       owned_canvas_(skia::AdoptRef(skia::CreatePlatformCanvas(0, 0, false))),
  60       canvas_(owned_canvas_.get()) {
  61 }
  62
  63 Canvas::~Canvas() {
  64 }
  65
  66 // static
  67 Canvas* Canvas::CreateCanvasWithoutScaling(SkCanvas* canvas,
  68                                            float image_scale) {
  69   return new Canvas(canvas, image_scale);
  70 }
  71
  72 void Canvas::RecreateBackingCanvas(const Size& size,
  73                                    float image_scale,
  74                                    bool is_opaque) {
  75   image_scale_ = image_scale;
  76   Size pixel_size = ToFlooredSize(ScaleSize(size, image_scale));
  77   owned_canvas_ = skia::AdoptRef(skia::CreatePlatformCanvas(pixel_size.width(),
  78                                                             pixel_size.height(),
  79                                                             is_opaque));
  80   canvas_ = owned_canvas_.get();
  81   SkScalar scale_scalar = SkFloatToScalar(image_scale);
  82   canvas_->scale(scale_scalar, scale_scalar);
  83 }
  84
  85 // static
  86 void Canvas::SizeStringInt(const base::string16& text,
  87                            const FontList& font_list,
  88                            int* width,
  89                            int* height,
  90                            int line_height,
  91                            int flags) {
  92   float fractional_width = *width;
  93   float factional_height = *height;
  94   SizeStringFloat(text, font_list, &fractional_width,
  95                   &factional_height, line_height, flags);
  96   *width = std::ceil(fractional_width);
  97   *height = std::ceil(factional_height);
  98 }
  99
 100 // static
 101 int Canvas::GetStringWidth(const base::string16& text,
 102                            const FontList& font_list) {
 103   int width = 0, height = 0;
 104   SizeStringInt(text, font_list, &width, &height, 0, NO_ELLIPSIS);
 105   return width;
 106 }
 107
 108 // static
 109 float Canvas::GetStringWidthF(const base::string16& text,
 110                               const FontList& font_list) {
 111   float width = 0, height = 0;
 112   SizeStringFloat(text, font_list, &width, &height, 0, NO_ELLIPSIS);
 113   return width;
 114 }
 115
 116 // static
 117 int Canvas::DefaultCanvasTextAlignment() {
 118   return base::i18n::IsRTL() ? TEXT_ALIGN_RIGHT : TEXT_ALIGN_LEFT;
 119 }
 120
 121 ImageSkiaRep Canvas::ExtractImageRep() const {
 122   // Make a bitmap to return, and a canvas to draw into it. We don't just want
 123   // to call extractSubset or the copy constructor, since we want an actual copy
 124   // of the bitmap.
 125   const SkISize size = canvas_->getDeviceSize();
 126   SkBitmap result;
 127   result.allocN32Pixels(size.width(), size.height());
 128
 129   canvas_->readPixels(&result, 0, 0);
 130   return ImageSkiaRep(result, image_scale_);
 131 }
 132
 133 void Canvas::DrawDashedRect(const Rect& rect, SkColor color) {
 134   // Create a 2D bitmap containing alternating on/off pixels - we do this
 135   // so that you never get two pixels of the same color around the edges
 136   // of the focus rect (this may mean that opposing edges of the rect may
 137   // have a dot pattern out of phase to each other).
 138   static SkColor last_color;
 139   static SkBitmap* dots = NULL;
 140   if (!dots || last_color != color) {
 141     int col_pixels = 32;
 142     int row_pixels = 32;
 143
 144     delete dots;
 145     last_color = color;
 146     dots = new SkBitmap;
 147     dots->allocN32Pixels(col_pixels, row_pixels);
 148     dots->eraseARGB(0, 0, 0, 0);
 149
 150     uint32_t* dot = dots->getAddr32(0, 0);
 151     for (int i = 0; i < row_pixels; i++) {
 152       for (int u = 0; u < col_pixels; u++) {
 153         if ((u % 2 + i % 2) % 2 != 0) {
 154           dot[i * row_pixels + u] = color;
 155         }
 156       }
 157     }
 158   }
 159
 160   // Make a shader for the bitmap with an origin of the box we'll draw. This
 161   // shader is refcounted and will have an initial refcount of 1.
 162   skia::RefPtr<SkShader> shader = skia::AdoptRef(
 163       SkShader::CreateBitmapShader(
 164           *dots, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode));
 165   // Assign the shader to the paint & release our reference. The paint will
 166   // now own the shader and the shader will be destroyed when the paint goes
 167   // out of scope.
 168   SkPaint paint;
 169   paint.setShader(shader.get());
 170
 171   DrawRect(Rect(rect.x(), rect.y(), rect.width(), 1), paint);
 172   DrawRect(Rect(rect.x(), rect.y() + rect.height() - 1, rect.width(), 1),
 173            paint);
 174   DrawRect(Rect(rect.x(), rect.y(), 1, rect.height()), paint);
 175   DrawRect(Rect(rect.x() + rect.width() - 1, rect.y(), 1, rect.height()),
 176            paint);
 177 }
 178
 179 void Canvas::Save() {
 180   canvas_->save();
 181 }
 182
 183 void Canvas::SaveLayerAlpha(uint8 alpha) {
 184   canvas_->saveLayerAlpha(NULL, alpha);
 185 }
 186
 187 void Canvas::SaveLayerAlpha(uint8 alpha, const Rect& layer_bounds) {
 188   SkRect bounds(RectToSkRect(layer_bounds));
 189   canvas_->saveLayerAlpha(&bounds, alpha);
 190 }
 191
 192 void Canvas::Restore() {
 193   canvas_->restore();
 194 }
 195
 196 void Canvas::ClipRect(const Rect& rect) {
 197   canvas_->clipRect(RectToSkRect(rect));
 198 }
 199
 200 void Canvas::ClipPath(const SkPath& path, bool do_anti_alias) {
 201   canvas_->clipPath(path, SkRegion::kIntersect_Op, do_anti_alias);
 202 }
 203
 204 bool Canvas::IsClipEmpty() const {
 205   return canvas_->isClipEmpty();
 206 }
 207
 208 bool Canvas::GetClipBounds(Rect* bounds) {
 209   SkRect out;
 210   bool has_non_empty_clip = canvas_->getClipBounds(&out);
 211   bounds->SetRect(out.left(), out.top(), out.width(), out.height());
 212   return has_non_empty_clip;
 213 }
 214
 215 void Canvas::Translate(const Vector2d& offset) {
 216   canvas_->translate(SkIntToScalar(offset.x()), SkIntToScalar(offset.y()));
 217 }
 218
 219 void Canvas::Scale(int x_scale, int y_scale) {
 220   canvas_->scale(SkIntToScalar(x_scale), SkIntToScalar(y_scale));
 221 }
 222
 223 void Canvas::DrawColor(SkColor color) {
 224   DrawColor(color, SkXfermode::kSrcOver_Mode);
 225 }
 226
 227 void Canvas::DrawColor(SkColor color, SkXfermode::Mode mode) {
 228   canvas_->drawColor(color, mode);
 229 }
 230
 231 void Canvas::FillRect(const Rect& rect, SkColor color) {
 232   FillRect(rect, color, SkXfermode::kSrcOver_Mode);
 233 }
 234
 235 void Canvas::FillRect(const Rect& rect,
 236                       SkColor color,
 237                       SkXfermode::Mode mode) {
 238   SkPaint paint;
 239   paint.setColor(color);
 240   paint.setStyle(SkPaint::kFill_Style);
 241   paint.setXfermodeMode(mode);
 242   DrawRect(rect, paint);
 243 }
 244
 245 void Canvas::DrawRect(const Rect& rect, SkColor color) {
 246   DrawRect(rect, color, SkXfermode::kSrcOver_Mode);
 247 }
 248
 249 void Canvas::DrawRect(const Rect& rect,
 250                       SkColor color,
 251                       SkXfermode::Mode mode) {
 252   SkPaint paint;
 253   paint.setColor(color);
 254   paint.setStyle(SkPaint::kStroke_Style);
 255   // Set a stroke width of 0, which will put us down the stroke rect path.  If
 256   // we set a stroke width of 1, for example, this will internally create a
 257   // path and fill it, which causes problems near the edge of the canvas.
 258   paint.setStrokeWidth(SkIntToScalar(0));
 259   paint.setXfermodeMode(mode);
 260
 261   DrawRect(rect, paint);
 262 }
 263
 264 void Canvas::DrawRect(const Rect& rect, const SkPaint& paint) {
 265   canvas_->drawIRect(RectToSkIRect(rect), paint);
 266 }
 267
 268 void Canvas::DrawPoint(const Point& p1, const SkPaint& paint) {
 269   canvas_->drawPoint(SkIntToScalar(p1.x()), SkIntToScalar(p1.y()), paint);
 270 }
 271
 272 void Canvas::DrawLine(const Point& p1, const Point& p2, SkColor color) {
 273   SkPaint paint;
 274   paint.setColor(color);
 275   paint.setStrokeWidth(SkIntToScalar(1));
 276   DrawLine(p1, p2, paint);
 277 }
 278
 279 void Canvas::DrawLine(const Point& p1, const Point& p2, const SkPaint& paint) {
 280   canvas_->drawLine(SkIntToScalar(p1.x()), SkIntToScalar(p1.y()),
 281                     SkIntToScalar(p2.x()), SkIntToScalar(p2.y()), paint);
 282 }
 283
 284 void Canvas::DrawCircle(const Point& center_point,
 285                         int radius,
 286                         const SkPaint& paint) {
 287   canvas_->drawCircle(SkIntToScalar(center_point.x()),
 288       SkIntToScalar(center_point.y()), SkIntToScalar(radius), paint);
 289 }
 290
 291 void Canvas::DrawRoundRect(const Rect& rect,
 292                            int radius,
 293                            const SkPaint& paint) {
 294   canvas_->drawRoundRect(RectToSkRect(rect), SkIntToScalar(radius),
 295                          SkIntToScalar(radius), paint);
 296 }
 297
 298 void Canvas::DrawPath(const SkPath& path, const SkPaint& paint) {
 299   canvas_->drawPath(path, paint);
 300 }
 301
 302 void Canvas::DrawFocusRect(const Rect& rect) {
 303   DrawDashedRect(rect, SK_ColorGRAY);
 304 }
 305
 306 void Canvas::DrawSolidFocusRect(const Rect& rect, SkColor color) {
 307   SkPaint paint;
 308   paint.setColor(color);
 309   paint.setStrokeWidth(SkIntToScalar(1));
 310   // Note: We cannot use DrawRect since it would create a path and fill it which
 311   // would cause problems near the edge of the canvas.
 312   int x1 = std::min(rect.x(), rect.right());
 313   int x2 = std::max(rect.x(), rect.right());
 314   int y1 = std::min(rect.y(), rect.bottom());
 315   int y2 = std::max(rect.y(), rect.bottom());
 316   DrawLine(Point(x1, y1), Point(x2, y1), paint);
 317   DrawLine(Point(x1, y2), Point(x2, y2), paint);
 318   DrawLine(Point(x1, y1), Point(x1, y2), paint);
 319   DrawLine(Point(x2, y1), Point(x2, y2 + 1), paint);
 320 }
 321
 322 void Canvas::DrawImageInt(const ImageSkia& image, int x, int y) {
 323   SkPaint paint;
 324   DrawImageInt(image, x, y, paint);
 325 }
 326
 327 void Canvas::DrawImageInt(const ImageSkia& image, int x, int y, uint8 a) {
 328   SkPaint paint;
 329   paint.setAlpha(a);
 330   DrawImageInt(image, x, y, paint);
 331 }
 332
 333 void Canvas::DrawImageInt(const ImageSkia& image,
 334                           int x,
 335                           int y,
 336                           const SkPaint& paint) {
 337   const ImageSkiaRep& image_rep = image.GetRepresentation(image_scale_);
 338   if (image_rep.is_null())
 339     return;
 340   const SkBitmap& bitmap = image_rep.sk_bitmap();
 341   float bitmap_scale = image_rep.scale();
 342
 343   canvas_->save();
 344   canvas_->scale(SkFloatToScalar(1.0f / bitmap_scale),
 345                  SkFloatToScalar(1.0f / bitmap_scale));
 346   canvas_->drawBitmap(bitmap,
 347                       SkFloatToScalar(x * bitmap_scale),
 348                       SkFloatToScalar(y * bitmap_scale),
 349                       &paint);
 350   canvas_->restore();
 351 }
 352
 353 void Canvas::DrawImageInt(const ImageSkia& image,
 354                           int src_x,
 355                           int src_y,
 356                           int src_w,
 357                           int src_h,
 358                           int dest_x,
 359                           int dest_y,
 360                           int dest_w,
 361                           int dest_h,
 362                           bool filter) {
 363   SkPaint p;
 364   DrawImageInt(image, src_x, src_y, src_w, src_h, dest_x, dest_y,
 365                dest_w, dest_h, filter, p);
 366 }
 367
 368 void Canvas::DrawImageInt(const ImageSkia& image,
 369                           int src_x,
 370                           int src_y,
 371                           int src_w,
 372                           int src_h,
 373                           int dest_x,
 374                           int dest_y,
 375                           int dest_w,
 376                           int dest_h,
 377                           bool filter,
 378                           const SkPaint& paint) {
 379   DrawImageIntHelper(image, src_x, src_y, src_w, src_h, dest_x, dest_y, dest_w,
 380                      dest_h, filter, paint, image_scale_, false);
 381 }
 382
 383 void Canvas::DrawImageIntInPixel(const ImageSkia& image,
 384                                  int src_x,
 385                                  int src_y,
 386                                  int src_w,
 387                                  int src_h,
 388                                  int dest_x,
 389                                  int dest_y,
 390                                  int dest_w,
 391                                  int dest_h,
 392                                  bool filter,
 393                                  const SkPaint& paint) {
 394   // Logic as below:-
 395   // 1. Translate the destination rectangle using the current translation
 396   //    values from the SkCanvas matrix stack.
 397   // 2. Save the current state of the canvas.
 398   // 3. Reset the scales and the translation values in the SkCanvas matrix
 399   //    stack top.
 400   // 4. Set the scale in gfx::Canvas instance to 1.0, 1.0.
 401   // 5. Draw the image.
 402   // 6. Restore the state of the canvas and the SkCanvas matrix stack.
 403   SkMatrix matrix = canvas_->getTotalMatrix();
 404
 405   SkRect destination_rect;
 406   destination_rect.set(SkIntToScalar(dest_x),
 407                        SkIntToScalar(dest_y),
 408                        SkIntToScalar(dest_x + dest_w),
 409                        SkIntToScalar(dest_y + dest_h));
 410   matrix.setScaleX(1.0f);
 411   matrix.setScaleY(1.0f);
 412   matrix.mapRect(&destination_rect, destination_rect);
 413
 414   Save();
 415
 416   // The destination is now in pixel values. No need for further translation.
 417   matrix.setTranslate(0, 0);
 418   canvas_->setMatrix(matrix);
 419
 420   DrawImageIntHelper(image,
 421                      src_x,
 422                      src_y,
 423                      src_w,
 424                      src_h,
 425                      SkScalarRoundToInt(destination_rect.x()),
 426                      SkScalarRoundToInt(destination_rect.y()),
 427                      SkScalarRoundToInt(destination_rect.width()),
 428                      SkScalarRoundToInt(destination_rect.height()),
 429                      filter,
 430                      paint,
 431                      image_scale_,
 432                      true);
 433
 434   // Restore the state of the canvas.
 435   Restore();
 436 }
 437
 438 void Canvas::DrawImageInPath(const ImageSkia& image,
 439                              int x,
 440                              int y,
 441                              const SkPath& path,
 442                              const SkPaint& paint) {
 443   const ImageSkiaRep& image_rep = image.GetRepresentation(image_scale_);
 444   if (image_rep.is_null())
 445     return;
 446
 447   SkMatrix matrix;
 448   matrix.setTranslate(SkIntToScalar(x), SkIntToScalar(y));
 449   skia::RefPtr<SkShader> shader = CreateImageRepShader(
 450       image_rep,
 451       SkShader::kRepeat_TileMode,
 452       matrix);
 453
 454   SkPaint p(paint);
 455   p.setShader(shader.get());
 456   canvas_->drawPath(path, p);
 457 }
 458
 459 void Canvas::DrawStringRect(const base::string16& text,
 460                             const FontList& font_list,
 461                             SkColor color,
 462                             const Rect& display_rect) {
 463   DrawStringRectWithFlags(text, font_list, color, display_rect,
 464                           DefaultCanvasTextAlignment());
 465 }
 466
 467 void Canvas::DrawStringRectWithFlags(const base::string16& text,
 468                                      const FontList& font_list,
 469                                      SkColor color,
 470                                      const Rect& display_rect,
 471                                      int flags) {
 472   DrawStringRectWithShadows(text, font_list, color, display_rect, 0, flags,
 473                             ShadowValues());
 474 }
 475
 476 void Canvas::TileImageInt(const ImageSkia& image,
 477                           int x,
 478                           int y,
 479                           int w,
 480                           int h) {
 481   TileImageInt(image, 0, 0, x, y, w, h);
 482 }
 483
 484 void Canvas::TileImageInt(const ImageSkia& image,
 485                           int src_x,
 486                           int src_y,
 487                           int dest_x,
 488                           int dest_y,
 489                           int w,
 490                           int h) {
 491   TileImageInt(image, src_x, src_y, 1.0f, 1.0f, dest_x, dest_y, w, h);
 492 }
 493
 494 void Canvas::TileImageInt(const ImageSkia& image,
 495                           int src_x,
 496                           int src_y,
 497                           float tile_scale_x,
 498                           float tile_scale_y,
 499                           int dest_x,
 500                           int dest_y,
 501                           int w,
 502                           int h) {
 503   if (!IntersectsClipRectInt(dest_x, dest_y, w, h))
 504     return;
 505
 506   const ImageSkiaRep& image_rep = image.GetRepresentation(image_scale_);
 507   if (image_rep.is_null())
 508     return;
 509
 510   SkMatrix shader_scale;
 511   shader_scale.setScale(SkFloatToScalar(tile_scale_x),
 512                         SkFloatToScalar(tile_scale_y));
 513   shader_scale.preTranslate(SkIntToScalar(-src_x), SkIntToScalar(-src_y));
 514   shader_scale.postTranslate(SkIntToScalar(dest_x), SkIntToScalar(dest_y));
 515
 516   skia::RefPtr<SkShader> shader = CreateImageRepShader(
 517       image_rep,
 518       SkShader::kRepeat_TileMode,
 519       shader_scale);
 520
 521   SkPaint paint;
 522   paint.setShader(shader.get());
 523   paint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
 524
 525   SkRect dest_rect = { SkIntToScalar(dest_x),
 526                        SkIntToScalar(dest_y),
 527                        SkIntToScalar(dest_x + w),
 528                        SkIntToScalar(dest_y + h) };
 529   canvas_->drawRect(dest_rect, paint);
 530 }
 531
 532 NativeDrawingContext Canvas::BeginPlatformPaint() {
 533   return skia::BeginPlatformPaint(canvas_);
 534 }
 535
 536 void Canvas::EndPlatformPaint() {
 537   skia::EndPlatformPaint(canvas_);
 538 }
 539
 540 void Canvas::Transform(const gfx::Transform& transform) {
 541   canvas_->concat(transform.matrix());
 542 }
 543
 544 Canvas::Canvas(SkCanvas* canvas, float image_scale)
 545     : image_scale_(image_scale),
 546       owned_canvas_(),
 547       canvas_(canvas) {
 548   DCHECK(canvas);
 549 }
 550
 551 bool Canvas::IntersectsClipRectInt(int x, int y, int w, int h) {
 552   SkRect clip;
 553   return canvas_->getClipBounds(&clip) &&
 554       clip.intersect(SkIntToScalar(x), SkIntToScalar(y), SkIntToScalar(x + w),
 555                      SkIntToScalar(y + h));
 556 }
 557
 558 bool Canvas::IntersectsClipRect(const Rect& rect) {
 559   return IntersectsClipRectInt(rect.x(), rect.y(),
 560                                rect.width(), rect.height());
 561 }
 562
 563 void Canvas::DrawImageIntHelper(const ImageSkia& image,
 564                                 int src_x,
 565                                 int src_y,
 566                                 int src_w,
 567                                 int src_h,
 568                                 int dest_x,
 569                                 int dest_y,
 570                                 int dest_w,
 571                                 int dest_h,
 572                                 bool filter,
 573                                 const SkPaint& paint,
 574                                 float image_scale,
 575                                 bool pixel) {
 576   DLOG_ASSERT(src_x + src_w < std::numeric_limits<int16_t>::max() &&
 577               src_y + src_h < std::numeric_limits<int16_t>::max());
 578   if (src_w <= 0 || src_h <= 0) {
 579     NOTREACHED() << "Attempting to draw bitmap from an empty rect!";
 580     return;
 581   }
 582
 583   if (!IntersectsClipRectInt(dest_x, dest_y, dest_w, dest_h))
 584     return;
 585
 586   float user_scale_x = static_cast<float>(dest_w) / src_w;
 587   float user_scale_y = static_cast<float>(dest_h) / src_h;
 588
 589   const ImageSkiaRep& image_rep = image.GetRepresentation(image_scale);
 590   if (image_rep.is_null())
 591     return;
 592
 593   SkRect dest_rect = { SkIntToScalar(dest_x),
 594                        SkIntToScalar(dest_y),
 595                        SkIntToScalar(dest_x + dest_w),
 596                        SkIntToScalar(dest_y + dest_h) };
 597
 598   if (src_w == dest_w && src_h == dest_h &&
 599       user_scale_x == 1.0f && user_scale_y == 1.0f &&
 600       image_rep.scale() == 1.0f && !pixel) {
 601     // Workaround for apparent bug in Skia that causes image to occasionally
 602     // shift.
 603     SkIRect src_rect = { src_x, src_y, src_x + src_w, src_y + src_h };
 604     const SkBitmap& bitmap = image_rep.sk_bitmap();
 605     canvas_->drawBitmapRect(bitmap, &src_rect, dest_rect, &paint);
 606     return;
 607   }
 608
 609   // Make a bitmap shader that contains the bitmap we want to draw. This is
 610   // basically what SkCanvas.drawBitmap does internally, but it gives us
 611   // more control over quality and will use the mipmap in the source image if
 612   // it has one, whereas drawBitmap won't.
 613   SkMatrix shader_scale;
 614   shader_scale.setScale(SkFloatToScalar(user_scale_x),
 615                         SkFloatToScalar(user_scale_y));
 616   shader_scale.preTranslate(SkIntToScalar(-src_x), SkIntToScalar(-src_y));
 617   shader_scale.postTranslate(SkIntToScalar(dest_x), SkIntToScalar(dest_y));
 618
 619   skia::RefPtr<SkShader> shader = CreateImageRepShaderForScale(
 620       image_rep,
 621       SkShader::kRepeat_TileMode,
 622       shader_scale,
 623       pixel ? 1.0f : image_rep.scale());
 624
 625   // Set up our paint to use the shader & release our reference (now just owned
 626   // by the paint).
 627   SkPaint p(paint);
 628   p.setFilterLevel(filter ? SkPaint::kLow_FilterLevel
 629                           : SkPaint::kNone_FilterLevel);
 630   p.setShader(shader.get());
 631
 632   // The rect will be filled by the bitmap.
 633   canvas_->drawRect(dest_rect, p);
 634 }
 635
 636 }  // namespace gfx