.NET7 ASP.NET WebAPI中IronOCR在Docker读取JPG图片报错求助

场景概述 #

Windows环境下运行完全正常，但部署到Docker后，对JPG图片字节数组执行OCR操作时触发报错，处理PDF文件则无异常。

核心代码 #

IronTesseract ocr = new IronTesseract();
using (OcrInput input = new OcrInput(data.ToArray())) // 报错位置
{
      input.Deskew();
      input.DeNoise();
      input.Invert();
                   
      OcrResult result = ocr.Read(input);
      return Task.FromResult(result.Text);
}

错误调用栈 #

Error in pixReadMemJpeg: function not present
Error in pixReadMem: jpeg: no pix returned
Failed to load image from memory.
      System.Exception: Failed to load image from memory.
       ---> System.Exception: Failed to load image from memory.
       ---> System.IO.IOException: Failed to load image from memory.
         at .(Byte[] )
         at IronOcr.OcrInput.Add(Byte[] imageAsByteArray, CropRectangle ContentArea)
         at IronOcr.OcrInput..ctor(Byte[] Bytes)

已尝试的Dockerfile配置 #

RUN apt-get update && apt-get install -y apt-utils libgdiplus libc6-dev
RUN apt-get install -y libjpeg-dev zlib1g-dev libpng-dev wget pkg-config gcc g++ make

RUN wget http://www.leptonica.org/source/leptonica-1.80.0.tar.gz && \
    tar -xvf leptonica-1.80.0.tar.gz && \
    cd leptonica-1.80.0 && \
    ./configure --disable-dependency-tracking && \
    make && \
    make install

补充信息 #

IronOCR官方建议使用的基础镜像：

FROM mcr.microsoft.com/dotnet/runtime:5.0-focal AS base

对应的官方示例配置：

FROM mcr.microsoft.com/dotnet/runtime:5.0-focal AS base
WORKDIR /app
# install necessary packages

RUN apt-get update && apt-get install -y apt-utils libgdiplus libc6-dev

当前使用的基础镜像为：

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base

1. 切换兼容的基础镜像 #

.NET7默认的aspnet镜像基于Ubuntu Jammy（22.04），与IronOCR依赖的Leptonica/Tesseract存在兼容性问题。将基础镜像替换为Ubuntu Focal（20.04）版本的.NET7镜像：

FROM mcr.microsoft.com/dotnet/aspnet:7.0-focal AS base
WORKDIR /app

2. 安装完整的预编译依赖库 #

无需手动编译Leptonica，直接安装系统兼容的预编译包，补充JPG处理所需的完整依赖：

RUN apt-get update && apt-get install -y --no-install-recommends \
    apt-utils \
    libgdiplus \
    libc6-dev \
    libjpeg-turbo8-dev \
    zlib1g-dev \
    libpng-dev \
    libtesseract4 \
    libleptonica-dev

3. 配置动态库加载路径（可选） #

若仍出现库找不到的情况，添加环境变量指定动态库路径：

ENV LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH

4. 验证依赖完整性 #

构建镜像后，可进入容器执行以下命令检查依赖是否正常加载：

ldd /usr/lib/x86_64-linux-gnu/liblept.so.5

内容的提问来源于stack exchange，提问作者Taufiq Abdur Rahman