Pillow进阶：图像处理实战技巧

Pillow 高级实战案例：图像处理的进阶应用

图像增强与滤镜效果

使用 Pillow 的 ImageEnhance 模块可以调整图像的亮度、对比度、色彩饱和度及锐度。通过调整参数，可以实现类似 Instagram 滤镜的效果。例如，增强对比度的代码如下：

from PIL import Image, ImageEnhance

image = Image.open("input.jpg")
enhancer = ImageEnhance.Contrast(image)
enhanced_image = enhancer.enhance(2.0)  # 对比度提升2倍
enhanced_image.save("output.jpg")

结合 ImageFilter 模块，还能添加高斯模糊、边缘检测等特效。例如，使用 GaussianBlur 实现柔化效果：

from PIL import ImageFilter

blurred_image = image.filter(ImageFilter.GaussianBlur(radius=5))
blurred_image.save("blurred.jpg")

多图像合成与蒙版操作

通过 Image.composite() 或 Image.blend() 可以实现图像叠加。例如，将两张图片按透明度混合：

image1 = Image.open("image1.png").convert("RGBA")
image2 = Image.open("image2.png").convert("RGBA")
blended = Image.blend(image1, image2, alpha=0.5)  # 50%透明度混合
blended.save("blended.png")

利用蒙版（Mask）可以精确控制合成区域。以下代码通过黑白蒙版指定合成范围：

mask = Image.open("mask.png").convert("L")  # 灰度蒙版
composite = Image.composite(image1, image2, mask)
composite.save("composite.png")

动态 GIF 生成

Pillow 支持将多帧图像合并为 GIF。通过逐帧处理并设置延迟时间，可以创建动画效果：

frames = []
for i in range(10):
    frame = Image.open(f"frame_{i}.png")
    frames.append(frame)

frames[0].save(
    "animation.gif",
    save_all=True,
    append_images=frames[1:],
    duration=100,  # 每帧100毫秒
    loop=0        # 无限循环
)

文字渲染与高级排版

结合 ImageDraw 模块，可以在图像上添加自定义文字。通过指定字体、颜色和位置实现复杂排版：

from PIL import ImageDraw, ImageFont

draw = ImageDraw.Draw(image)
font = ImageFont.truetype("arial.ttf", size=40)
draw.text(
    (50, 50), 
    "Hello Pillow", 
    fill="white", 
    font=font,
    stroke_width=2,
    stroke_fill="black"
)
image.save("text_overlay.jpg")

支持多行文本的对齐和换行处理，通过 textbbox 计算文本区域实现居中布局。

图像批处理与自动化

通过遍历目录批量处理图像，适合大规模任务。以下代码将所有 JPEG 图像调整为指定尺寸：

import os
from PIL import Image

input_dir = "input_images"
output_dir = "output_images"
os.makedirs(output_dir, exist_ok=True)

for filename in os.listdir(input_dir):
    if filename.endswith(".jpg"):
        img = Image.open(os.path.join(input_dir, filename))
        img_resized = img.resize((800, 600))
        img_resized.save(os.path.join(output_dir, filename))

结合 ThreadPoolExecutor 可加速批处理任务。

颜色空间转换与直方图分析

Pillow 支持 RGB、HSV、CMYK 等颜色空间转换。例如，将图像转为灰度并分析直方图：

gray_image = image.convert("L")
histogram = gray_image.histogram()

通过 ImageOps 模块的 equalize() 可进行直方图均衡化，增强低对比度图像。

高级裁剪与几何变换

使用 Image.transform() 实现透视变换，结合 ImageOps 的 crop() 和 pad() 处理非矩形区域。例如，校正倾斜的文档图像：

from PIL import ImageOps

corrected = image.transform(
    (new_width, new_height),
    Image.Transform.PERSPECTIVE,
    [x0, y0, x1, y1, x2, y2, x3, y3]
)

通过 EXIF 数据自动旋转图像，解决手机拍摄的方向问题。

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