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通过将 Python 实现的功能编译成 WebAssembly (Wasm),可以创建一个完全跨平台的、可被任何编程语言调用的库。
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具体步骤演示(以图像处理库为例)1. Python 功能实现 (image_processor.py)
---------------------------------
from PIL import Image
import numpy as np
def resize_image(image_data, width, height):
"""调整图像尺寸"""
img = Image.frombytes('RGB', (width, height), image_data)
img = img.resize((width // 2, height // 2)) # 缩小50%
return img.tobytes()
def apply_filter(image_data, width, height, filter_name):
"""应用图像滤镜"""
img = Image.frombytes('RGB', (width, height), image_data)
if filter_name == "grayscale":
img = img.convert("L")
elif filter_name == "edge_detect":
# 简单的边缘检测
arr = np.array(img)
gray = np.mean(arr, axis=2)
edges = np.abs(np.gradient(gray)[0]) + np.abs(np.gradient(gray)[1])
img = Image.fromarray(np.uint8(edges))
return img.tobytes(), img.width, img.height
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2. 定义 WIT 接口 (image.wit)-------------------------
package example:image
interface processor {
/// 调整图像尺寸
/// @param image-data: 原始图像二进制数据
/// @param width: 原始宽度
/// @param height: 原始高度
/// @return: 调整后的图像数据
resize: func(
image-data: list<u8>,
width: u32,
height: u32
) -> list<u8>
/// 应用图像滤镜
/// @param filter-name: 滤镜名称 (grayscale/edge_detect)
/// @return: tuple(处理后的图像数据, 新宽度, 新高度)
apply-filter: func(
image-data: list<u8>,
width: u32,
height: u32,
filter-name: string
) -> tuple<list<u8>, u32, u32>
}
world image-processor {
export processor
}
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3. 编译为 Wasm 组件
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# 安装编译工具
pip install pyodide-build wit-bindgen
# 创建虚拟环境(包含依赖)
python -m venv .env
source .env/bin/activate
pip install pillow numpy
# 编译为 Wasm
pyodide build --output image_processor.wasm image_processor.py
# 嵌入 WIT 接口
wasm-tools component embed image.wit image_processor.wasm -o image_processor_component.wasm
# 优化大小 (可选)
wasm-opt -O3 image_processor_component.wasm -o image_processor_optimized.wasm
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4. 其他语言调用示例
-------------------
#include <stdio.h>
#include <wasmtime.h>
void process_image() {
// 初始化Wasm引擎
wasm_engine_t *engine = wasm_engine_new();
wasm_store_t *store = wasm_store_new(engine);
// 加载Wasm组件
wasm_module_t *module = wasm_module_from_file(store, "image_processor_optimized.wasm");
wasm_instance_t *instance = wasm_instance_new(store, module, NULL);
// 获取函数
wasm_func_t *resize_func = wasm_instance_export_get_func(instance, "example:image/processor.resize");
// 准备图像数据 (伪代码)
uint8_t *image_data = load_jpeg("input.jpg", &width, &height);
wasm_val_t args[3] = {
WASM_PTR_VAL(image_data),
WASM_I32_VAL(width),
WASM_I32_VAL(height)
};
// 调用函数
wasm_val_t results[1];
wasm_func_call(resize_func, args, 3, results, 1);
// 获取结果
uint8_t *resized_data = results[0].of.ptr;
save_jpeg("output.jpg", resized_data, width/2, height/2);
}
----------------------
JavaScript 调用
------------------
// 浏览器中运行
async function processImage() {
// 加载Wasm模块
const response = await fetch('image_processor_optimized.wasm');
const buffer = await response.arrayBuffer();
const module = await WebAssembly.compile(buffer);
// 实例化
const instance = await WebAssembly.instantiate(module);
// 获取Canvas图像数据
const canvas = document.getElementById('my-canvas');
const ctx = canvas.getContext('2d');
const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
// 调用边缘检测
const [processedData, newWidth, newHeight] =
instance.exports['example:image/processor.apply-filter'](
imageData.data,
canvas.width,
canvas.height,
"edge_detect"
);
// 显示结果
const newImage = new ImageData(
new Uint8ClampedArray(processedData),
newWidth,
newHeight
);
ctx.putImageData(newImage, 0, 0);
}
----------------------
Rust 调用
-------------
use wasmtime::{Store, Module, Instance, Func, TypedFunc};
use std::fs;
fn main() {
let wasm_bytes = fs::read("image_processor_optimized.wasm").unwrap();
let engine = wasmtime::Engine::default();
let module = Module::from_binary(&engine, &wasm_bytes).unwrap();
let mut store = Store::new(&engine, ());
let instance = Instance::new(&mut store, &module, &[]).unwrap();
// 获取函数
let apply_filter: TypedFunc<((Vec<u8>, u32, u32, String), (Vec<u8>, u32, u32))> =
instance.get_typed_func(&mut store, "example:image/processor.apply-filter").unwrap();
// 加载图像
let image_data = std::fs::read("input.jpg").unwrap();
let (width, height) = (800, 600); // 实际应从图像获取
// 应用滤镜
let (processed, new_width, new_height) =
apply_filter.call(&mut store, (image_data, width, height, "grayscale".to_string())).unwrap();
// 保存结果
std::fs::write("output.jpg", processed).unwrap();
}
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真正的跨语言调用
同一 .wasm 文件可被 40+ 语言调用
无需为每种语言编写绑定
Python崩溃不会影响宿主程序
无法访问宿主文件系统(除非显式授权)
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