使用 IronOCR 處理作物區域和矩形

Curtis Chau

更新:6月 1, 2025

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如何使用 IronOCR 設定 PDF 的內容區域？

內容區域和 PDF

OcrInput.LoadPdf和LoadPdfPage方法都提供了新增ContentArea 的選項。

問題是－PDF 檔案的大小不是以像素為單位的，但內容區域通常是以像素為單位的，我該如何知道我的內容區域有多大？

選項 1

OcrInput.TargetDPI預設值為 225 - 這決定了 PDF 影像的像素大小。 IronOCR 會看到這則訊息。

方案二（理想使用場景）

使用OcrInput.LoadPdf()載入您的 PDF 範本。
使用OcrInput.GetPages()取得輸入框的寬度和高度。
使用OcrInput.GetPages().First().ToBitmap()取得 OCR 引擎將讀取的確切影像。
現在您可以測量匯出影像中內容區域的像素大小。
目標座標可用於特定的 OCR 區域（請參閱最終結果）。

取得您的資訊：

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

Private ocr = New IronTesseract()
Using 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
	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

$vbLabelText $csharpLabel

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

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

	' 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

$vbLabelText $csharpLabel

API 參考： OcrInput | OcrInput.Page