使用IronOCR裁剪區域和矩形

Curtis Chau

Updated: 2026年6月29日

如何使用IronOCR在PDF上設定內容區域？

內容區域和PDF

OcrInput.LoadPdf 和 LoadPdfPage 方法都可以選擇新增內容區域。

問題 - 如何知道我的內容區域有多大，因為PDF不是以像素為單位，但內容區域通常用它們來測量？

選項 1

OcrInput.TargetDPI 的預設值是225 - 這決定了PDF圖像的像素大小。 IronOCR會讀取這個。

選項 2（理想使用案例）

在您的PDF模板中使用 OcrInput.LoadPdf()。
使用 OcrInput.GetPages() 來獲取輸入的寬度和高度。
使用 OcrInput.GetPages().First().ToBitmap() 來獲取OCR引擎將讀取的精確圖像。
您現在可以從匯出的圖像中以像素測量內容區域。
目標坐標可用於特定的OCR區域（參見最終結果）。

要獲取您的資訊：

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

最終結果：

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 Reference: OcrInput | OcrInput.Page