| /* |
| * Copyright 2014 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "SkPatchUtils.h" |
| |
| // size in pixels of each partition per axis, adjust this knob |
| static const int kPartitionSize = 15; |
| |
| /** |
| * Calculate the approximate arc length given a bezier curve's control points. |
| */ |
| static SkScalar approx_arc_length(SkPoint* points, int count) { |
| if (count < 2) { |
| return 0; |
| } |
| SkScalar arcLength = 0; |
| for (int i = 0; i < count - 1; i++) { |
| arcLength += SkPoint::Distance(points[i], points[i + 1]); |
| } |
| return arcLength; |
| } |
| |
| SkISize SkPatchUtils::GetLevelOfDetail(const SkPatch& patch, const SkMatrix* matrix) { |
| |
| SkPoint mapPts[12]; |
| matrix->mapPoints(mapPts, patch.getControlPoints(), 12); |
| |
| // Approximate length of each cubic. |
| SkPoint pts[4]; |
| patch.getTopPoints(pts); |
| matrix->mapPoints(pts, 4); |
| SkScalar topLength = approx_arc_length(pts, 4); |
| |
| patch.getBottomPoints(pts); |
| matrix->mapPoints(pts, 4); |
| SkScalar bottomLength = approx_arc_length(pts, 4); |
| |
| patch.getLeftPoints(pts); |
| matrix->mapPoints(pts, 4); |
| SkScalar leftLength = approx_arc_length(pts, 4); |
| |
| patch.getRightPoints(pts); |
| matrix->mapPoints(pts, 4); |
| SkScalar rightLength = approx_arc_length(pts, 4); |
| |
| // Level of detail per axis, based on the larger side between top and bottom or left and right |
| int lodX = static_cast<int>(SkMaxScalar(topLength, bottomLength) / kPartitionSize); |
| int lodY = static_cast<int>(SkMaxScalar(leftLength, rightLength) / kPartitionSize); |
| |
| return SkISize::Make(SkMax32(4, lodX), SkMax32(4, lodY)); |
| } |