用鼠标旋转图像

这里涉及的到图像旋转后，方向的计算。我也不是很明白。先记录下来再说。

#_*_coding:utf-8 _*_

import pygame
from pygame.locals import *
from sys import exit
from gameobjects.vector2 import Vector2
from math import *

background_image_filename=‘./images/sea.jpg‘
sprite_image_filename=‘./images/fish.png‘

import pygame
from pygame.locals import *
from sys import exit
pygame.init()
# 让pygame完全控制鼠标
pygame.mouse.set_visible(False)
pygame.event.set_grab(True)

screen=pygame.display.set_mode((640,480),0,32)
background=pygame.image.load(background_image_filename).convert()
sprite=pygame.image.load(sprite_image_filename)
clock=pygame.time.Clock()

sprite_pos = Vector2(200, 150)   # 初始位置
sprite_speed = 300.     # 每秒前进的像素数（速度）
sprite_rotation = 0.      # 初始角度
sprite_rotation_speed = 360. # 每秒转动的角度数（转速）

while True:

    for event in pygame.event.get():
        if event.type == QUIT:
            exit()

    pressed_keys = pygame.key.get_pressed()

    rotation_direction = 0.
    movement_direction = 0.
    # 通过移动偏移量计算转动
    rotation_direction = pygame.mouse.get_rel()[0]/5.0
    #更改角度
    if pressed_keys[K_LEFT]:
        rotation_direction+=1
    if pressed_keys[K_RIGHT]:
        rotation_direction-=1
    #前进 后退
    if pressed_keys[K_UP]:
        movement_direction+=1
    if pressed_keys[K_DOWN]:
        movement_direction-=1

    screen.blit(background,(0,0))

    #获得一条转向后的鱼
    rotated_sprite=pygame.transform.rotate(sprite,sprite_rotation)
    #获得转向后的矩形
    w,h=rotated_sprite.get_size()
    sprite_draw_pos=Vector2(sprite_pos.x-w/2,sprite_pos.y-h/2)
    screen.blit(rotated_sprite,sprite_draw_pos)

    time_passed = clock.tick()
    time_passed_seconds = time_passed / 1000.0

    # 图片的转向速度也需要和行进速度一样，通过时间来控制
    sprite_rotation += rotation_direction * sprite_rotation_speed * time_passed_seconds

    # 获得前进（x方向和y方向），这两个需要一点点三角的知识
    heading_x = sin(sprite_rotation * pi / 180.)
    heading_y = cos(sprite_rotation * pi / 180.)
    # 转换为单位速度向量
    heading = Vector2(heading_x, heading_y)
    # 转换为速度
    heading *= movement_direction

    sprite_pos += heading * sprite_speed * time_passed_seconds

    pygame.display.update()