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59 lines
2.0 KiB
Markdown
59 lines
2.0 KiB
Markdown
# CanvasAgg演示
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此示例展示了如何直接使用AGG后端创建图像，对于希望完全控制其代码而不使用pylot界面来管理图形、图形关闭等的Web应用程序开发人员来说，这可能是有用的。
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**注意：**没有必要避免使用图形前端 - 只需将后端设置为“Agg”就足够了。
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在这个例子中，我们展示了如何将画布的内容保存到文件，以及如何将它们提取到一个字符串，该字符串可以传递给PIL或放在一个numpy数组中。 后一种功能允许例如使用没有文档到磁盘的cp脚本。
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```python
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from matplotlib.backends.backend_agg import FigureCanvasAgg
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from matplotlib.figure import Figure
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import numpy as np
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fig = Figure(figsize=(5, 4), dpi=100)
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# A canvas must be manually attached to the figure (pyplot would automatically
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# do it). This is done by instantiating the canvas with the figure as
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# argument.
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canvas = FigureCanvasAgg(fig)
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# Do some plotting.
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ax = fig.add_subplot(111)
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ax.plot([1, 2, 3])
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# Option 1: Save the figure to a file; can also be a file-like object (BytesIO,
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# etc.).
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fig.savefig("test.png")
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# Option 2: Save the figure to a string.
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canvas.draw()
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s, (width, height) = canvas.print_to_buffer()
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# Option 2a: Convert to a NumPy array.
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X = np.fromstring(s, np.uint8).reshape((height, width, 4))
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# Option 2b: Pass off to PIL.
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from PIL import Image
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im = Image.frombytes("RGBA", (width, height), s)
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# Uncomment this line to display the image using ImageMagick's `display` tool.
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# im.show()
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```
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## 参考
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此示例中显示了以下函数，方法，类和模块的使用：
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```python
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import matplotlib
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matplotlib.backends.backend_agg.FigureCanvasAgg
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matplotlib.figure.Figure
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matplotlib.figure.Figure.add_subplot
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matplotlib.figure.Figure.savefig
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matplotlib.axes.Axes.plot
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```
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## 下载这个示例
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- [下载python源码: canvasagg.py](https://matplotlib.org/_downloads/canvasagg.py)
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- [下载Jupyter notebook: canvasagg.ipynb](https://matplotlib.org/_downloads/canvasagg.ipynb) |