Android 自定义圆形取色盘

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概述
这是一个自定义色盘，根据点，直线和圆的几何学加上hsv颜色模型完成

技术点
几何：
圆的标准方程式：
(x-a)²+(y-b)²=r²
直线一般方程式：

已知直线上的两点P1(X1,Y1) P2(X2,Y2)， P1 P2两点不重合。
AX+BY+C=0
A = Y2 - Y1
B = X1 - X2
C = X2*Y1 - X1*Y2点与圆的位置关系：
点在圆内、点在圆上、点在圆外。假设圆的半径为r，点到圆心的距离为d，则有：d＜r点在圆内，d=r点在圆上，d＞r点在圆外。
点P（x1,y1) 与圆(x-a)²+(y-b)²=r²的位置关系：
当(x-a)²+(y-b)²＞r²时，则点P在圆外。
当(x-a)²+(y-b)²=r²时，则点P在圆上。
当(x-a)²+(y-b)²＜r²时，则点P在圆内。
直线的斜率：
一条直线与某平面直角坐标系横轴正半轴方向的夹角的正切值即该直线相对于该坐标系的斜率
斜率 k=tanα（α倾斜角）
与x轴垂直的直线不存在斜率
直线的斜率公式为：k=y2-y1）/（x2-x1）或（y1-y2）/（x1-x2）
象限：
记

（x,y) 是象限中的一点
第一象限中的点：x > 0, y > 0
第二象限中的点：x < 0, y > 0
第三象限中的点：x < 0, y < 0
第四象限中的点：x > 0, y < 0
值得注意的是原点和坐标轴上的点不属于任何象限。
解方程:

Android：

自定义View、ComposeShader、SweepGradient、RadialGradient、Paint。

上源码
代码都比较简单这里就不介绍了

1 class RoundColorPaletteHSV360 constructor(context: Context, attrs: AttributeSet?, defStyleAttr:Int): View(context,attrs,defStyleAttr) {
  2 
  3   constructor(context: Context):this(context,null,0)
  4 
  5   constructor(context: Context,attrs: AttributeSet?):this(context,attrs,0)
  6 
  7   //取色范围半径
  8   var radius:Float = 0f
  9     private set(value){
 10       field = value-stroke-gap-colorRadius
 11     }
 12 
 13   //取色圆半径
 14   var colorRadius = 50f
 15     set(value){
 16       if (value >= 0)
 17         field = value
 18     }
 19 
 20   //取色圆边框半径
 21   var colorStroke = 8f
 22     set(value){
 23       if (value >= 0)
 24         field = value
 25     }
 26 
 27   //取色圆边框颜色
 28   var colorStrokeColor = Color.BLACK
 29 
 30   //取色颜色
 31   var color = Color.WHITE
 32 
 33   //边框半径
 34   var stroke = 24f
 35     set(value){
 36       if (value >= 0)
 37         field = value
 38     }
 39 
 40   //边框颜色
 41   var strokeColor = Color.YELLOW
 42 
 43   //间隙半径
 44   var gap = 4f
 45     set(value){
 46       if (value >= 0)
 47         field = value
 48     }
 49 
 50   var isOutOfBounds:Boolean = false
 51 
 52   private val paint = Paint()
 53   private val colors1:IntArray
 54   private val positions1 :FloatArray
 55   private val colors2:IntArray
 56   private val positions2 :FloatArray
 57   private var xColor: Float = 0f
 58   private var yColor: Float = 0f
 59   private var colorChangeCallBack: ColorChangeCallBack? = null
 60 
 61   init {
 62 //    <declare-styleable name="RoundColorPaletteHSV360">
 63 //    <attr name="colorRadius" format="dimension"/>
 64 //    <attr name="colorStroke" format="dimension"/>
 65 //    <attr name="gap" format="dimension"/>
 66 //    <attr name="stroke" format="dimension"/>
 67 //    <attr name="colorStrokeColor" format="color"/>
 68 //    <attr name="strokeColor" format="color"/>
 69 //    <attr name="isOutOfBounds" format="boolean"/>
 70 //    </declare-styleable>
 71     val  typedArray = context.obtainStyledAttributes(attrs, R.styleable.RoundColorPaletteHSV360)
 72     colorRadius = typedArray.getDimension(R.styleable.RoundColorPaletteHSV360_colorRadius,50f)
 73     colorStroke = typedArray.getDimension(R.styleable.RoundColorPaletteHSV360_colorStroke,8f)
 74     gap = typedArray.getDimension(R.styleable.RoundColorPaletteHSV360_gap,4f)
 75     stroke = typedArray.getDimension(R.styleable.RoundColorPaletteHSV360_stroke,24f)
 76     colorStrokeColor = typedArray.getColor(R.styleable.RoundColorPaletteHSV360_colorStrokeColor,Color.BLACK)
 77     strokeColor = typedArray.getColor(R.styleable.RoundColorPaletteHSV360_strokeColor,Color.YELLOW)
 78     isOutOfBounds = typedArray.getBoolean(R.styleable.RoundColorPaletteHSV360_isOutOfBounds,false)
 79     typedArray.recycle()
 80 
 81     val colorCount1 = 360
 82     val colorCount2 = 255
 83     val colorAngleStep = 360 / colorCount1
 84     positions1 = FloatArray(colorCount1+1){i-> i/(colorCount1*1f)}
 85     var hsv = floatArrayOf(0f, 1f, 1f)
 86     colors1 = IntArray(colorCount1+1){ i->
 87       hsv[0] = 360 - i * colorAngleStep % 360f
 88       Color.HSVToColor(hsv)
 89     }
 90     hsv = floatArrayOf(0f, 0f, 1f)
 91     positions2 = FloatArray(colorCount2+1){i-> i/(colorCount2*1f)}
 92     colors2 = IntArray(colorCount2+1){ i->
 93       Color.HSVToColor(255 * (colorCount2 -i) / colorCount2 , hsv)
 94     }
 95 
 96   }
 97 
 98   override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
 99     val width = MeasureSpec.getSize(widthMeasureSpec)/2f
100     val height = MeasureSpec.getSize(heightMeasureSpec)/2f
101     radius = if(width-height<0) width else height
102     super.onMeasure(widthMeasureSpec, heightMeasureSpec)
103   }
104 
105   @SuppressLint("DrawAllocation")
106   override fun onDraw(canvas: Canvas?) {
107     createColorWheel(canvas)
108     createColorRadius(canvas,xColor,yColor)
109     super.onDraw(canvas)
110   }
111 
112   //色盘
113   private fun createColorWheel(canvas: Canvas?){
114     paint.reset()
115     paint.isAntiAlias = true
116     paint.shader = ComposeShader(
117       SweepGradient(
118         width / 2f,
119         height / 2f,
120         colors1,
121         positions1
122       ), RadialGradient(
123         width / 2f,
124         height / 2f,
125         radius-colorRadius,
126         colors2,
127         positions2,
128         Shader.TileMode.CLAMP
129       ),  PorterDuff.Mode.SRC_OVER)
130     canvas?.drawCircle(width / 2f,height / 2f,radius,paint)
131     paint.shader = null
132     paint.style = Paint.Style.STROKE
133     paint.strokeWidth = stroke.toFloat()
134     paint.color = strokeColor
135     canvas?.drawCircle(width / 2f,height / 2f,radius+gap+stroke/2,paint)
136   }
137 
138   //取色圆
139   private fun createColorRadius(canvas: Canvas?, rx: Float, ry: Float){
140     var x = rx
141     var y = ry
142     if(x==0f || y==0f ){
143       x = width / 2f
144       y = height / 2f
145     }
146     paint.reset()
147     paint.isAntiAlias = true
148     paint.color = color
149     canvas?.drawCircle(x,y,colorRadius,paint)
150     paint.style = Paint.Style.STROKE
151     paint.color = colorStrokeColor
152     paint.strokeWidth = colorStroke
153     canvas?.drawCircle(x,y,colorRadius+colorStroke/2,paint)
154   }
155 
156   fun setColorChangeCallBack(colorChangeCallBack: ColorChangeCallBack){
157     this.colorChangeCallBack = colorChangeCallBack
158   }
159 
160   override fun onTouchEvent(event: MotionEvent?): Boolean {
161     event?.let {
162       val pointToCircle = pointToCircle(it.x, it.y)
163       if( pointToCircle <= radius - if(isOutOfBounds) 0f else (colorRadius-colorStroke)){
164         xColor =  it.x
165         yColor =  it.y
166         color =  Color.HSVToColor(floatArrayOf((angdeg(it.x,it.y)),pointToCircle/radius,1f))
167         colorChangeCallBack?.onChange(color)
168       }else{
169         findPoint( it.x, it.y)
170       }
171       invalidate()
172     }
173     return true
174   }
175 
176   //点到圆心距离
177   private fun pointToCircle(x: Float = width / 2f, y: Float = height / 2f ) =
178     sqrt((x - width / 2f)*(x - width / 2f) + (y-height / 2f)*(y-height / 2f))
179 
180   //离目标最近的点 待开发
181   private fun findPoint(x1: Float = width / 2f, y1: Float = height / 2f ){
182 //    直线一般方程
183 //    以圆心为坐标0，0 重新计算点（a，b）坐标
184     val a = y1 - height / 2f
185     val b = x1 - width / 2f
186     val r = radius - if(isOutOfBounds) 0f else (colorRadius-colorStroke)
187     //r^2/((b/a)^2+1)的开平方
188     yColor = sqrt( (r * r) / ((b / a) * (b / a) + 1))
189     //判断开平方的正负值
190     if(a<0) yColor = -yColor
191     xColor =  (b*yColor)/a + width / 2f
192     yColor += height / 2f
193     color =  Color.HSVToColor(floatArrayOf((angdeg(xColor,yColor)),1f,1f))
194     colorChangeCallBack?.onChange(color)
195 
196   }
197 
198 
199   //角度
200   private fun angdeg(x: Float = width / 2f, y: Float = height / 2f ):Float{
201     var angdeg = 0
202 
203     //特殊角度, 与x轴垂直不存在斜率
204     if(x - width / 2f == 0f && y - height / 2f < 0){
205       angdeg = 90
206     }else{
207       //到圆心的斜率
208       val k = ((y-height / 2f)*(y-height / 2f))/((x - width / 2f)*(x - width / 2f))
209       //二分法
210       var min = 0.00
211       var max = 90.00
212       while(max-min>1){
213         val deg = min + (max - min) / 2
214         if(k>tan(toRadians(deg))) min = deg else max = deg
215       }
216       angdeg = (max-1).toInt()
217     }
218 
219     if((x - width / 2f <= 0f && y - height / 2f <= 0f)) {//第二象限 90~180
220       angdeg = 180 - angdeg
221     }else if((x - width / 2f <= 0f && y - height / 2f >= 0f)) {//第三象限 180~270
222       angdeg += 180
223     }else if((x - width / 2f >= 0f && y - height / 2f >= 0f)) {//第四象限 270~360
224       angdeg = 360 - angdeg
225     }
226 
227     return angdeg.toFloat()
228   }
229 
230   interface ColorChangeCallBack{
231     fun onChange(@ColorInt color: Int)
232   }
233 }

View Code# 圆形取色盘
#### 仓库地址
https://gitee.com/yangguizhong/circular-color-plate

#### 安装教程
gradle 7.0以上的在 settings.gradle 添加：
```
dependencyResolutionManagement {
repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
repositories {
      google()
      mavenCentral()
      maven {url "https://gitee.com/yangguizhong/circular-color-plate/raw/master"}
      jcenter() // Warning: this repository is going to shut down soon
}
}
```
gradle 7.0以下的在根 build.gradle 添加：
```
allprojects {
repositories {
      google()
      mavenCentral()
      maven {url "https://gitee.com/yangguizhong/circular-color-plate/raw/master"}
}
}
```
build.gradle 添加：
```
implementation 'com.xiaotie.colorPicker:colorPicker:1.0.0'
```

#### 使用说明

```
<com.wifiled.ipixels.view.RoundColorPaletteHSV360
         android:id="@+id/color_picker"
         android:layout_width="300dp"
         android:layout_height="300dp"
         app:gap="1dp"//取色背景和背景边框的间隙
         app:colorRadius="20dp"//取色圆的半径
         app:colorStroke="3dp"//取色圆的边框宽度
         app:stroke="8dp"//背景边框的宽度
         app:strokeColor="#FFF7A6"//背景边框的颜色
         app:isOutOfBounds="true"//是否超出边框
         app:colorStrokeColor="#2E3C3C"//取色圆的边框宽度
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent" />
```
```
colorPickerView.setColorChangeCallBack(object:RoundColorPaletteHSV360.ColorChangeCallBack{
            override fun onChange(color: Int) {
               //返回的颜色
            }
})
```

[Android] Android 自定义圆形取色盘

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