注意

跳转至底部以下载完整示例代码。

矢量图栅格化#

栅格化将矢量图转换为栅格图像（像素）。它可以加快渲染速度并为大型数据集生成更小的文件，但代价是固定分辨率。

是否使用栅格化可以根据每个绘图元素单独指定。这有助于减小大型绘图元素的文件大小，同时保持矢量图对其他绘图元素（如坐标轴和文本）的优势。例如，通过栅格化可以大大简化复杂的pcolormesh或contourf。栅格化设置仅影响矢量后端，如 PDF、SVG 或 PS。

栅格化默认是禁用的。有两种方法可以启用它，这两种方法也可以结合使用

栅格化绘图元素的存储大小和分辨率由其物理尺寸以及传递给savefig的dpi参数值决定。

注意

HTML 文档中显示的此示例图片并非矢量图。因此，它无法展示栅格化效果。请在本地运行此示例并检查生成的图形文件。

import matplotlib.pyplot as plt
import numpy as np

d = np.arange(100).reshape(10, 10)  # the values to be color-mapped
x, y = np.meshgrid(np.arange(11), np.arange(11))

theta = 0.25*np.pi
xx = x*np.cos(theta) - y*np.sin(theta)  # rotate x by -theta
yy = x*np.sin(theta) + y*np.cos(theta)  # rotate y by -theta

fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2, layout="constrained")

# pcolormesh without rasterization
ax1.set_aspect(1)
ax1.pcolormesh(xx, yy, d)
ax1.set_title("No Rasterization")

# pcolormesh with rasterization; enabled by keyword argument
ax2.set_aspect(1)
ax2.set_title("Rasterization")
ax2.pcolormesh(xx, yy, d, rasterized=True)

# pcolormesh with an overlaid text without rasterization
ax3.set_aspect(1)
ax3.pcolormesh(xx, yy, d)
ax3.text(0.5, 0.5, "Text", alpha=0.2,
         va="center", ha="center", size=50, transform=ax3.transAxes)
ax3.set_title("No Rasterization")

# pcolormesh with an overlaid text without rasterization; enabled by zorder.
# Setting the rasterization zorder threshold to 0 and a negative zorder on the
# pcolormesh rasterizes it. All artists have a non-negative zorder by default,
# so they (e.g. the text here) are not affected.
ax4.set_aspect(1)
m = ax4.pcolormesh(xx, yy, d, zorder=-10)
ax4.text(0.5, 0.5, "Text", alpha=0.2,
         va="center", ha="center", size=50, transform=ax4.transAxes)
ax4.set_rasterization_zorder(0)
ax4.set_title("Rasterization z$<-10$")

# Save files in pdf and eps format
plt.savefig("test_rasterization.pdf", dpi=150)
plt.savefig("test_rasterization.eps", dpi=150)

if not plt.rcParams["text.usetex"]:
    plt.savefig("test_rasterization.svg", dpi=150)
    # svg backend currently ignores the dpi
No Rasterization, Rasterization, No Rasterization, Rasterization z$<-10$
The PostScript backend does not support transparency; partially transparent artists will be rendered opaque.

参考

本示例展示了以下函数、方法、类和模块的使用

脚本总运行时间： (0 分 2.912 秒)

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