RTEditor/src/main/java/com/onegravity/rteditor/media/crop/HighlightView.java
void handleMotion(int edge, float dx, float dy) {
        Rect r = computeLayout();
        if (edge == GROW_NONE) {
            return;
        } else if (edge == MOVE) {
            // Convert to image space before sending to moveBy().
            moveBy(dx * (mCropRect.width() / r.width()),
                    dy * (mCropRect.height() / r.height()));
        } else {
            if (((GROW_LEFT_EDGE | GROW_RIGHT_EDGE) & edge) == 0) {
                dx = 0;
            }

            if (((GROW_TOP_EDGE | GROW_BOTTOM_EDGE) & edge) == 0) {
                dy = 0;
            }

            // Convert to image space before sending to growBy().
            float xDelta = dx * (mCropRect.width() / r.width());
            float yDelta = dy * (mCropRect.height() / r.height());
            growBy((((edge & GROW_LEFT_EDGE) != 0) ? -1 : 1) * xDelta,
                    (((edge & GROW_TOP_EDGE) != 0) ? -1 : 1) * yDelta);
        }
    }
void handleMotion(int edge, float dx, float dy) {
        Rect r = computeLayout();
        if (edge == GROW_NONE) {
            return;
        } else if (edge == MOVE) {
            // Convert to image space before sending to moveBy().
            moveBy(dx * (mCropRect.width() / r.width()),
                    dy * (mCropRect.height() / r.height()));
        } else {
            if (((GROW_LEFT_EDGE | GROW_RIGHT_EDGE) & edge) == 0) {
                dx = 0;
            }

            if (((GROW_TOP_EDGE | GROW_BOTTOM_EDGE) & edge) == 0) {
                dy = 0;
            }

            // Convert to image space before sending to growBy().
            float xDelta = dx * (mCropRect.width() / r.width());
            float yDelta = dy * (mCropRect.height() / r.height());
            growBy((((edge & GROW_LEFT_EDGE) != 0) ? -1 : 1) * xDelta,
                    (((edge & GROW_TOP_EDGE) != 0) ? -1 : 1) * yDelta);
        }
    }
The "edge" parameter specifies which edges the user is dragging.