使用 IronOCR 处理作物区域和矩形

Curtis Chau

Updated: 2026年6月29日

如何使用 IronOCR 设置 PDF 的内容区域？

内容区域和 PDF

LoadPdfPage方法都可以选择添加一个ContentArea。

问题是——PDF 文件的大小不是以像素为单位的，但内容区域通常是以像素为单位的，我该如何知道我的内容区域有多大？

选项 1

OcrInput.TargetDPI默认值为225 - 它决定PDF图像的像素大小。 IronOCR 会看到这条信息。

方案二（理想使用场景）

使用OcrInput.LoadPdf()与您的PDF模板。
使用OcrInput.GetPages()获取输入的宽度和高度。
使用OcrInput.GetPages().First().ToBitmap()获取OCR引擎将读取的确切图像。
现在您可以测量导出图像中内容区域的像素大小。
目标坐标可用于特定的 OCR 区域（参见最终结果）。

获取您的信息：

using System.Linq;  // Needed for First()
using IronOcr;

var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    // Load the PDF document
    input.LoadPdf("example.pdf");
    
    // Save the first page as a bitmap to measure it
    input.GetPages().First().ToBitmap().SaveAs("measure-me.bmp");
    
    // Get the dimensions of the first page
    var width = input.GetPages().First().Width;
    var height = input.GetPages().First().Height;

    // Optionally, output the dimensions to understand the scale
    Console.WriteLine($"Width: {width}px, Height: {height}px");
}

using System.Linq;  // Needed for First()
using IronOcr;

var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    // Load the PDF document
    input.LoadPdf("example.pdf");
    
    // Save the first page as a bitmap to measure it
    input.GetPages().First().ToBitmap().SaveAs("measure-me.bmp");
    
    // Get the dimensions of the first page
    var width = input.GetPages().First().Width;
    var height = input.GetPages().First().Height;

    // Optionally, output the dimensions to understand the scale
    Console.WriteLine($"Width: {width}px, Height: {height}px");
}

Imports System.Linq ' Needed for First()
Imports IronOcr

Dim ocr As New IronTesseract()
Using input As New OcrInput()
    ' Load the PDF document
    input.LoadPdf("example.pdf")

    ' Save the first page as a bitmap to measure it
    input.GetPages().First().ToBitmap().SaveAs("measure-me.bmp")

    ' Get the dimensions of the first page
    Dim width = input.GetPages().First().Width
    Dim height = input.GetPages().First().Height

    ' Optionally, output the dimensions to understand the scale
    Console.WriteLine($"Width: {width}px, Height: {height}px")
End Using

Imports System.Linq ' Needed for First()
Imports IronOcr

Dim ocr As New IronTesseract()
Using input As New OcrInput()
    ' Load the PDF document
    input.LoadPdf("example.pdf")

    ' Save the first page as a bitmap to measure it
    input.GetPages().First().ToBitmap().SaveAs("measure-me.bmp")

    ' Get the dimensions of the first page
    Dim width = input.GetPages().First().Width
    Dim height = input.GetPages().First().Height

    ' Optionally, output the dimensions to understand the scale
    Console.WriteLine($"Width: {width}px, Height: {height}px")
End Using

最终结果：

using IronOcr;
using IronSoftware.Drawing; // Needed for Rectangle

var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    // Define the content area rectangle with specific pixel coordinates
    var contentArea = new Rectangle
    { 
        X = 215, 
        Y = 1250, 
        Height = 280, 
        Width = 1335 
    };  //<-- the area you want in px
    
    // Load the specific content area of the PDF
    input.LoadPdf("example.pdf", contentArea: contentArea);
    
    // Perform OCR on the defined content area
    var result = ocr.Read(input);

    // Optionally, print the OCR result
    Console.WriteLine(result.Text);
}

using IronOcr;
using IronSoftware.Drawing; // Needed for Rectangle

var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    // Define the content area rectangle with specific pixel coordinates
    var contentArea = new Rectangle
    { 
        X = 215, 
        Y = 1250, 
        Height = 280, 
        Width = 1335 
    };  //<-- the area you want in px
    
    // Load the specific content area of the PDF
    input.LoadPdf("example.pdf", contentArea: contentArea);
    
    // Perform OCR on the defined content area
    var result = ocr.Read(input);

    // Optionally, print the OCR result
    Console.WriteLine(result.Text);
}

Imports IronOcr
Imports IronSoftware.Drawing ' Needed for Rectangle

Dim ocr As New IronTesseract()
Using input As New OcrInput()
    ' Define the content area rectangle with specific pixel coordinates
    Dim contentArea As New Rectangle With {
        .X = 215,
        .Y = 1250,
        .Height = 280,
        .Width = 1335
    } '<-- the area you want in px

    ' Load the specific content area of the PDF
    input.LoadPdf("example.pdf", contentArea:=contentArea)

    ' Perform OCR on the defined content area
    Dim result = ocr.Read(input)

    ' Optionally, print the OCR result
    Console.WriteLine(result.Text)
End Using

Imports IronOcr
Imports IronSoftware.Drawing ' Needed for Rectangle

Dim ocr As New IronTesseract()
Using input As New OcrInput()
    ' Define the content area rectangle with specific pixel coordinates
    Dim contentArea As New Rectangle With {
        .X = 215,
        .Y = 1250,
        .Height = 280,
        .Width = 1335
    } '<-- the area you want in px

    ' Load the specific content area of the PDF
    input.LoadPdf("example.pdf", contentArea:=contentArea)

    ' Perform OCR on the defined content area
    Dim result = ocr.Read(input)

    ' Optionally, print the OCR result
    Console.WriteLine(result.Text)
End Using

API 参考： OcrInput|OcrInput.Page