1，优化代码

Author: FlyJingFish

library/src/main/java/com/flyjingfish/shapeimageviewlib/ShapeImageView.java

@@ -344,44 +344,29 @@ private void drawBgShape(Canvas canvas) {
                 angle = 360 + angle;
             }
             float x0, y0, x1, y1;
-            if (angle >= 0 && angle <= 45) {
-                float percent = angle / 45;
-                x0 = width / 2 + width / 2 * percent;
-                y0 = 0;
-            } else if (angle <= 90) {
-                float percent = (angle - 45) / 45;
-                x0 = width;
-                y0 = height / 2 * percent;
-            } else if (angle <= 135) {
-                float percent = (angle - 90) / 45;
-                x0 = width;
-                y0 = height / 2 * percent + height / 2;
-            } else if (angle <= 180) {
-                float percent = (angle - 135) / 45;
-                x0 = width / 2 + width / 2 * (1-percent);
-                y0 = height;
-            } else if (angle <= 225) {
-                float percent = (angle - 180) / 45;
-                x0 = width / 2 - width / 2 * percent;
-                y0 = height;
-            } else if (angle <= 270) {
-                float percent = (angle - 225) / 45;
-                x0 = 0;
-                y0 = height - height / 2 * percent;
-            } else if (angle <= 315) {
-                float percent = (angle - 270) / 45;
-                x0 = 0;
-                y0 = height / 2 - height / 2 * percent;
-            } else {
-                float percent = (angle - 315) / 45;
-                x0 = width / 2 * percent;
-                y0 = 0;
+            if ((angle >= 0 && angle < 90) || (angle >=180 && angle < 270)){
+                x0 = (float) (width/2 + Math.signum(90 - angle) * height/2f * Math.tan(Math.toRadians(angle - (angle >= 180?180:0))));
+                if (x0 >= width || x0 <= 0){
+                    x0 = angle < 90?width:0;
+                    y0 = (float) (height/2 - Math.signum(90 - angle) * width/2f * Math.tan(Math.toRadians((angle >= 180?270:90) - angle)));
+                }else {
+                    y0 = angle < 90?0:height;
+                }
+            }else {
+                y0 = (float) (height/2f + Math.signum(180 - angle) * width/2f * Math.tan(Math.toRadians(angle - (angle < 180?90:270))));
+                if (y0 >= height || y0 <= 0){
+                    y0 = angle < 180?height:0;
+                    x0 = (float) (width/2 + Math.signum(180 - angle) * height/2f * Math.tan(Math.toRadians((angle < 180?180:360) - angle)));
+                }else {
+                    x0 = angle < 180?width:0;
+                }
             }
             x1 = width - x0;
             y1 = height - y0;
             LinearGradient linearGradient = new LinearGradient(x0, y0, x1, y1, gradientColors, gradientPositions, Shader.TileMode.CLAMP);
             mBgPaint.setShader(linearGradient);
         }
+        mDrawBgPath.reset();
         if (bgShapeType == ShapeType.OVAL) {
             mDrawBgPath.addOval(mBgRectF, Path.Direction.CCW);
         } else {