Android自定义有限制区域的图例角度自识别涂鸦工具类完结篇

//设置着色器
public Shader setShader(Shader shader) {
    // If mShader changes, cached value of native shader aren't valid, since
    // old shader's pointer may be reused by another shader allocation later
    if (mShader != shader) {
        mNativeShader = -1;
        // Release any native references to the old shader content
        nSetShader(mNativePaint, 0);
    }
    // Defer setting the shader natively until getNativeInstance() is called
    mShader = shader;
    return shader;
}

//设置着色器
paint.shader = BitmapShader(
    bitmap,
    Shader.TileMode.REPEAT,
    Shader.TileMode.REPEAT
)

//通过反正切得到角度
val first = allPoints[0] //第一个点
val last = allPoints[allPoints.size-1] //最后一个点
val angle = atan2((last.y - first.y).toDouble(),(last.x - first.x).toDouble()) * (180 / Math.PI)

//旋转+缩放
val dstbmp = Bitmap.createBitmap(
    bmp, 0, 0, bmp.width, bmp.height,
    Matrix().apply {
        // 缩放原图
        postScale(0.5f, 0.5f)
        // 向左旋转45度，参数为正则向右旋转
        postRotate(defaultDegrees, bmp.width / 2f, bmp.height / 2f)
    }, true
)
//设置着色器
paint.shader = BitmapShader(
    dstbmp,
    Shader.TileMode.REPEAT,
    Shader.TileMode.REPEAT
)