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可以通过撤销操作来将第二张图片的状态更改回第一张图片的状态。
具体步骤如下:
- 当用户进行了操作后,将该操作记录在一个操作栈中。
- 当用户想要撤销操作时,从操作栈中取出最后一次操作,并将该操作的反操作记录在一个撤销操作栈中。
- 执行该操作的反操作,使得当前状态回退到操作前的状态。
- 将该操作的反操作记录在一个重做操作栈中。
- 如果用户想要重做操作,从重做操作栈中取出最后一次操作,并执行该操作。
- 将该操作记录到操作栈中,使得该操作可以被撤销。 以下是 Python 代码示例:
class ImageEditor:
def __init__(self):
self.stack = [] # 操作栈
self.undo_stack = [] # 撤销操作栈
self.redo_stack = [] # 重做操作栈
self.current_state = ImageState() # 当前状态
def perform_operation(self, operation: Operation):
"""执行操作"""
self.stack.append(operation)
self.current_state = operation.execute(self.current_state)
def undo(self):
"""撤销操作"""
if self.stack:
operation = self.stack.pop()
undo_operation = operation.undo()
self.current_state = undo_operation.execute(self.current_state)
self.undo_stack.append(undo_operation)
def redo(self):
"""重做操作"""
if self.redo_stack:
operation = self.redo_stack.pop()
self.current_state = operation.execute(self.current_state)
self.stack.append(operation)
def save_image(self):
"""保存当前状态"""
with open("image_state.pickle", "wb") as f:
pickle.dump(self.current_state, f)
def load_image(self):
"""加载之前保存的状态"""
with open("image_state.pickle", "rb") as f:
self.current_state = pickle.load(f)
其中,Operation 是一个操作的抽象类,包含了执行操作和撤销操作的抽象方法。
class Operation(ABC):
@abstractmethod
def execute(self, state: ImageState) -> ImageState:
pass
@abstractmethod
def undo(self) -> Operation:
pass
ImageState 是图像的状态类,包含了图像的信息。
class ImageState:
def __init__(self):
self.image = None
self.width = None
self.height = None
def __eq__(self, other):
return isinstance(other, ImageState) and \
self.image == other.image and \
self.width == other.width and \
self.height == other.height
下面是一个具体的操作类 CropOperation,用于裁剪图像。在执行操作时,会将操作前的状态保存到操作对象中,撤销操作时,会将操作前的状态恢复。
class CropOperation(Operation):
def __init__(self, x0, y0, x1, y1):
self.x0 = x0
self.y0 = y0
self.x1 = x1
self.y1 = y1
self.old_state = None
def execute(self, state: ImageState) -> ImageState:
self.old_state = state
state.image = state.image[self.y0:self.y1, self.x0:self.x1]
state.width = self.x1 - self.x0
state.height = self.y1 - self.y0
return state
def undo(self) -> Operation:
return CropOperation(0, 0, self.old_state.width, self.old_state.height)