/** Returns a shader that generates a linear gradient between the twospecified points.<p />CreateLinear returns a shader with a reference count of 1.The caller should decrement the shader's reference count when done with the shader.It is an error for count to be < 2.@param  pts The start and end points for the gradient.@param  colors  The array[count] of colors, to be distributed between the two points@param  pos     May be NULL. array[count] of SkScalars, or NULL, of the relative position ofeach corresponding color in the colors array. If this is NULL,the the colors are distributed evenly between the start and end point.If this is not null, the values must begin with 0, end with 1.0, andintermediate values must be strictly increasing.@param  count   Must be >=2. The number of colors (and pos if not NULL) entries. @param  mode    The tiling mode@param  mapper  May be NULL. Callback to modify the spread of the colors.*/static SkShader* CreateLinear(  const SkPoint pts[2],const SkColor colors[], const SkScalar pos[], int count,SkShader::TileMode mode,SkUnitMapper* mapper = NULL);

//画到屏幕上
void Flip()
{HDC dc = GetDC(g_hWnd);SetDIBitsToDevice(dc, 0, 0, 800, 480, 0, 0, 0, 800, pskBitmap->getPixels(), lpbmi, DIB_RGB_COLORS);ReleaseDC(g_hWnd,dc);
}void PaintShader()
{SkPaint paint;paint.setAntiAlias(true);//paint.setStyle(SkPaint::kStroke_Style);//paint.setStrokeWidth(SkScalarHalf(SkIntToScalar(3)));//paint.setStyle(SkPaint::kFill_Style);SkPoint p = SkPoint::Make(50,50);SkPoint q = SkPoint::Make(100,50);SkPoint pts[] ={p,q};SkScalar t,temp,x,y;SkColor colors[] ={SK_ColorRED,SK_ColorGREEN,SK_ColorBLUE,SK_ColorWHITE,SK_ColorBLACK};//红、绿、蓝、白、黑，这些宏的alpha值都是FF，即不透明SkShader *shader ;shader =SkGradientShader::CreateLinear(pts,colors,NULL,SK_ARRAY_COUNT(colors),SkShader::kMirror_TileMode);//pts决定Gradient的起始点和走向，以及过渡完gClors的颜色需要的像素距离paint.setShader(shader);shader->unref();SkRect r = {0,0,SkIntToScalar(200),SkIntToScalar(100)};// 如果r范围小于pts，则只显示完整过渡colors需要像素的一部分，如果大于就会按mode重复//kMirror_TileMode就是红绿蓝白黑+白蓝绿红+绿蓝白黑+白...重复pskCanvas->drawRect(r,paint);shader =SkGradientShader::CreateLinear(pts,colors,NULL,SK_ARRAY_COUNT(colors),SkShader::kRepeat_TileMode);paint.setShader(shader);shader->ref();r.setLTRB(0,SkIntToScalar(110),SkIntToScalar(200),SkIntToScalar(210));pskCanvas->drawRect(r,paint);shader =SkGradientShader::CreateLinear(pts,colors,NULL,SK_ARRAY_COUNT(colors),SkShader::kClamp_TileMode);paint.setShader(shader);shader->ref();r.setLTRB(0,SkIntToScalar(220),SkIntToScalar(200),SkIntToScalar(320));pskCanvas->drawRect(r,paint);}void MyLButtonDown(POINT pt)
{PaintShader();Flip();}

 SkPoint p = SkPoint::Make(0,50);SkPoint q = SkPoint::Make(800,50);SkPoint pts[] ={p,q};SkColor colors[] ={SK_ColorRED,SK_ColorGREEN,SK_ColorBLUE,SK_ColorWHITE,SK_ColorBLACK};SkScalar scalars[] ={0.0, 0.2, 0.2, 0.3,1.0};//红绿过渡占20%，绿蓝没有过渡，蓝白过渡占10%，白黑过渡70%（对应值的差）SkShader *shader ;shader =SkGradientShader::CreateLinear(pts,colors,scalars,SK_ARRAY_COUNT(colors),SkShader::kMirror_TileMode);//pts决定Gradient的起始点和走向，以及过渡完gClors的颜色需要的像素距离paint.setShader(shader);shader->unref();SkRect r = {0,0,SkIntToScalar(800),SkIntToScalar(100)};