image-extraction

Image Extraction Example

This example demonstrates how to extract images from PDF documents using GxPDF.

Features Demonstrated

1. Extract all images from a document

   • Get all images from all pages
   • Save to disk automatically

2. Extract images from specific page

   • Target specific pages
   • Control output location

3. Process image metadata

   • Get image dimensions
   • Check color space and encoding
   • Access raw image data

Usage

# Extract all images from a PDF
go run main.go document.pdf

# Extract to specific directory
go run main.go document.pdf ./extracted_images

# Help
go run main.go

API Reference

Document-level Extraction

doc, _ := gxpdf.Open("document.pdf")
defer doc.Close()

// Get all images from all pages
images := doc.GetImages()

// With error handling
images, err := doc.GetImagesWithError()

Page-level Extraction

page := doc.Page(0) // First page

// Get all images from this page
images := page.GetImages()

// With error handling
images, err := page.GetImagesWithError()

Image Operations

for _, img := range images {
    // Get metadata
    fmt.Printf("%dx%d, %s\n", img.Width(), img.Height(), img.ColorSpace())

    // Save to file (format determined by extension)
    img.SaveToFile("output.jpg")  // JPEG
    img.SaveToFile("output.png")  // PNG

    // Convert to Go image for processing
    goImg, _ := img.ToGoImage()
}

Supported Image Formats

GxPDF can extract images with the following encodings:

• DCTDecode (JPEG) - Direct extraction, no re-encoding
• FlateDecode (zlib) - Decompressed and converted
• Uncompressed - Direct extraction

Color Spaces

• DeviceRGB - RGB color images
• DeviceGray - Grayscale images
• DeviceCMYK - CMYK images (conversion to RGB coming soon)
• Indexed - Palette-based images (expansion coming soon)

Output Formats

Images can be saved as:

• JPEG (.jpg, .jpeg) - Best for photos and DCTDecode images
• PNG (.png) - Best for lossless images and transparency

For DCTDecode images saved as JPEG, the original compressed data is used directly, preserving quality without re-encoding.

Example Output

=== Example 1: Extract All Images from Document ===
Found 5 images in document
  Saved: image_0.jpg (800x600, DeviceRGB, /DCTDecode)
  Saved: image_1.jpg (1024x768, DeviceRGB, /DCTDecode)
  Saved: image_2.png (200x200, DeviceGray, /FlateDecode)
  Saved: image_3.jpg (640x480, DeviceRGB, /DCTDecode)
  Saved: image_4.png (100x100, DeviceRGB, /FlateDecode)

=== Example 2: Extract Images from Specific Page ===
Found 2 images on page 1
  Saved: page1_image_0.jpg (800x600)
  Saved: page1_image_1.jpg (1024x768)

=== Example 3: Process Images (Metadata Only) ===
Page 1:
  Image 0:
    Name: /Im1
    Dimensions: 800x600 pixels
    Color Space: DeviceRGB
    Bits per Component: 8
    Filter: /DCTDecode
    Go Image Bounds: (0,0)-(800,600)

Notes

• Images are extracted in the order they appear in the PDF's resource dictionary
• Inline images are not yet supported (coming soon)
• CMYK to RGB conversion is not yet implemented
• Indexed color space expansion is not yet implemented

See Also

• Image Embedding Example - How to add images to PDFs
• GxPDF Documentation - Full library documentation