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/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkPatchGrid_DEFINED
#define SkPatchGrid_DEFINED
#include "SkCanvas.h"
#include "SkPatchUtils.h"
#include "SkXfermode.h"
/**
* Class that represents a grid of patches. Adjacent patches share their corners and a color is
* specified at each one of them. The colors are bilinearly interpolated across the patch.
*
* This implementation defines a bidimensional array of patches. There are 3 arrays to store the
* control points of the patches to avoid storing repeated data since there are several points
* shared between adjacent patches.
*
* The array fCornerPts stores the corner control points of the patches.
* The array fHrzPts holds the intermidiate control points of the top and bottom curves of a patch.
* The array fVrtPts holds the intermidiate control points of the left and right curves of a patch.
* The array fCornerColors holds the corner colors in the same format as fCornerPts.
* The array fTexCoords holds the texture coordinates in the same format as fCornerpts.
*
* fCornerPts fHrzPts fVrtPts
* -------------- ------------------- --------------
* | C0 | C1 | C2 | | H0 | H1 | H2 | H3 | | V0 | V1 | V2 |
* -------------- ------------------ ---------------
* | C3 | C4 | C5 | | H4 | H5 | H6 | H7 | | V4 | V5 | V6 |
* -------------- ------------------- --------------
* | C6 | C7 | C8 | | H8 | H9 | H10| H11| | V6 | V7 | V8 |
* -------------- ------------------- --------------
* | V9 | V10| V11|
* --------------
*
* With the above configuration we would have a 2x2 grid of patches:
* H0 H1 H2 H3
* / \/ \
* C0-------C1-------C2
* /| | |\
* v0 | v1 | v2
* v3 | V4 | v5
* \| | |/
* C3-H4-H5-C4-H6-H7-C5
* /| | |\
* v6 | v7 | v8
* v9 | v10 | v11
* \| | |/
* C6-------C7-------C8
* \ / \ /
* H8 H9 H10 H11
*
* When trying to get a patch at a certain position it justs builds it with the corresponding
* points.
* When adding a patch it tries to add the points at their corresponding position trying to comply
* with the adjacent points or overwriting them.
*
* Based the idea on the SVG2 spec for mesh gradients in which a grid of patches is build as in the
* the following example:
* <meshGradient x="100" y="100">
* <meshRow>
* <meshPatch>
* <stop .../>
* Up to four stops in first patch. See details below.
* </meshPatch>
* <meshPatch>
* Any number of meshPatches in row.
* </meshPatch>
* </meshRow>
* <meshRow>
* Any number of meshRows, each with the same number of meshPatches as in the first row.
* </meshRow>
* </meshGradient>
*/
class SkPatchGrid {
public:
enum VertexType {
kNone_VertexType = 0X00,
kColors_VertexType = 0x01,
kTexs_VertexType = 0x02,
kColorsAndTexs_VertexType = 0x03
};
SkPatchGrid(int rows = 0, int cols = 0, VertexType flags = kNone_VertexType,
SkXfermode* xfer = nullptr);
~SkPatchGrid();
/**
* Add a patch at location (x,y) overwriting the previous patch and shared points so they
* mantain C0 connectivity.
* The control points must be passed in a clockwise order starting at the top left corner.
* The colors and texCoords are the values at the corners of the patch which will be bilerp
* across it, they must also be in counterclockwise order starting at the top left corner.
*/
bool setPatch(int x, int y, const SkPoint cubics[12], const SkColor colors[4],
const SkPoint texCoords[4]);
/**
* Get patch at location (x,y). If cubics, colors or texCoords is not nullptr it sets patch's
* array with its corresponding values.
* The function returns false if the cubics parameter is nullptr or if the (x,y) coordinates are
* not within the range of the grid.
*/
bool getPatch(int x, int y, SkPoint cubics[12], SkColor colors[4], SkPoint texCoords[4]) const;
/**
* Resets the grid of patches to contain rows and cols of patches.
*/
void reset(int rows, int cols, VertexType flags, SkXfermode* xMode);
/**
* Draws the grid of patches. The patches are drawn starting at patch (0,0) drawing columns, so
* for a 2x2 grid the order would be (0,0)->(0,1)->(1,0)->(1,1). The order follows the order
* of the parametric coordinates of the coons patch.
*/
void draw(SkCanvas* canvas, SkPaint& paint);
/**
* Get the dimensions of the grid of patches.
*/
SkISize getDimensions() const {
return SkISize::Make(fCols, fRows);
}
private:
int fRows, fCols;
VertexType fModeFlags;
SkPoint* fCornerPts;
SkColor* fCornerColors;
SkPoint* fTexCoords;
SkPoint* fHrzCtrlPts;
SkPoint* fVrtCtrlPts;
SkXfermode* fXferMode;
};
#endif
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