What’s new in GroupDocs.Signature for Python 26.1 (January 2026)

ID Category Summary
SIGNATURENET‑5528 ✨ Feature 圖像數位簽章支援與驗證（針對 PNG 與 JPG 的最低有效位元隱寫）。
SIGNATURENET‑5445 ✨ Feature 條碼與 QR Code 簽章預覽的自適應渲染 – 可明確控制寬度/高度。
SIGNATURENET‑5479 ✨ Feature 條碼與 QR Code 預覽圖像的旋轉支援。
SIGNATURENET‑5478 ✨ Feature 新增對 APNG 與 TGA 圖像格式的處理，以用於基於圖像的簽章。
SIGNATURENET‑5500 ⚡ Enhancement LINQ 風格的查詢最佳化，用於簽章搜尋與驗證（謂詞過濾）。
SIGNATURENET‑5480 ⚡ Enhancement 條碼/QR 預覽的背景透明度支援。
SIGNATURENET‑5477 ⚡ Enhancement 數位簽章的覆蓋圖像支援，可同時設定背景色（前景圖像旗標）。
SIGNATURENET‑5422 ⚡ Enhancement 移除不安全的加密演算法（RC2、DES、TripleDES 以及弱 AES 模式）。
SIGNATURENET‑5555 🐞 Bug Fix 修正 Linux 上處理 DOC 檔案時 GeneratePreview() 的型別初始化子例外。

以下是一段針對最具影響力變更的簡短技術說明。

1. Image digital signature (steganography)

  • 簽章隱藏在 PNG/JPG 像素的最低有效位元中。
  • 支援密碼保護、串流相容，且可用於任意尺寸 ≥ 8 × 8 px 的圖像。

Signing an image

import groupdocs.signature as gs
import groupdocs.signature.options as gso

input_file  = "image.png"
output_file = "signed_image.png"
password    = "MySecurePassword123"

# Sign the image
with gs.Signature(input_file) as signature:
    sign_options = gso.ImageDigitalSignOptions()
    sign_options.password = password

    sign_result = signature.sign(output_file, sign_options)

    if sign_result.succeeded and len(sign_result.succeeded) > 0:
        print("Image signed successfully!")
        print(f"Signatures added: {len(sign_result.succeeded)}")

Verifying a signed image

import groupdocs.signature as gs
import groupdocs.signature.options as gso

signed_file = "signed_image.png"
password    = "MySecurePassword123"

with gs.Signature(signed_file) as signature:
    verify_options = gso.ImageDigitalVerifyOptions()
    verify_options.password = password
    verify_options.detection_threshold_percent = 75  # optional 0‑100%

    verify_result = signature.verify(verify_options)

    if verify_result.is_valid:
        print("Digital signature is valid!")
        print(f"Verified signatures: {len(verify_result.succeeded)}")
    else:
        print("Digital signature is invalid or not found.")

Advanced validation (full data extraction)

with gs.Signature("signed_image.png") as signature:
    verify_options = gso.ImageDigitalVerifyOptions()
    verify_options.password = "MySecurePassword123"
    verify_options.use_full_data_extraction = True
    verify_options.detection_threshold_percent = 85

    verify_result = signature.verify(verify_options)

    if verify_result.is_valid and verify_options.detected_probability is not None:
        print(f"Signature detected with {verify_options.detected_probability}% probability")

2. Adaptive rendering for Barcode & QR Code previews

開發者現在可以為預覽產生指定精確的 width 與 height，消除先前「自動尺寸」的不一致情況。

import groupdocs.signature as gs
import groupdocs.signature.options as gso
import uuid

# QR code options
qr_sign_options = gso.QrCodeSignOptions("GROUP DOCS", gs.QrCodeTypes.QR)
qr_sign_options.width  = 250
qr_sign_options.height = 270
qr_sign_options.fore_color = gs.Color.red
qr_sign_options.code_text_alignment = gs.CodeTextAlignment.BELOW
qr_sign_options.text = "GROUP DOCS"

# Preview generation
preview_options = gso.PreviewSignatureOptions(
    qr_sign_options,
    create_signature_stream,   # user‑provided delegate
    release_signature_stream   # user‑provided delegate
)
preview_options.signature_id   = str(uuid.uuid4())
preview_options.preview_format = gso.PreviewSignatureOptions.PreviewFormats.PNG

gs.Signature.generate_signature_preview(preview_options)

3. Rotation support for Barcode & QR previews

在條碼/QR 選項上設定 rotation_angle（度）即可產生旋轉後的預覽。

import groupdocs.signature as gs
import groupdocs.signature.options as gso
import uuid

barcode_sign_options = gso.BarcodeSignOptions("GROUP DOCS", gs.BarcodeTypes.MaxiCode)
barcode_sign_options.width          = 400
barcode_sign_options.height         = 400
barcode_sign_options.fore_color     = gs.Color.red
barcode_sign_options.code_text_alignment = gs.CodeTextAlignment.BELOW
barcode_sign_options.text           = "GROUP DOCS"
barcode_sign_options.rotation_angle = 45   # rotate 45°

preview_options = gso.PreviewSignatureOptions(
    barcode_sign_options,
    create_signature_stream,
    release_signature_stream
)
preview_options.signature_id   = str(uuid.uuid4())
preview_options.preview_format = gso.PreviewSignatureOptions.PreviewFormats.PNG

gs.Signature.generate_signature_preview(preview_options)

4. New image format support – APNG & TGA

APNG（動態 PNG）與 TGA（Targa）檔案現在可作為圖像簽章使用，插入、預覽與驗證方式與 PNG/JPG 完全相同。

5. Background transparency for Barcode/QR previews

在條碼/QR 選項上設定 transparency（0 – 1）屬性，即可產生具有透明畫布的預覽。

barcode_sign_options = gso.BarcodeSignOptions("GROUP DOCS", gs.BarcodeTypes.Codabar)
barcode_sign_options.width  = 400
barcode_sign_options.height = 400
barcode_sign_options.fore_color = gs.Color.red
barcode_sign_options.code_text_alignment = gs.CodeTextAlignment.BELOW
barcode_sign_options.text = "GROUP DOCS"
barcode_sign_options.transparency = 0.5   # 50 % transparent background

preview_options = gso.PreviewSignatureOptions(
    barcode_sign_options,
    create_signature_stream,
    release_signature_stream
)
preview_options.signature_id = str(uuid.uuid4())
preview_options.preview_format = gso.PreviewSignatureOptions.PreviewFormats.PNG

gs.Signature.generate_signature_preview(preview_options)

6. Overlay image support for digital signatures

PdfDigitalSignatureAppearance 現在同時支援覆蓋圖像 與 背景色，且不會遮蔽圖像。可透過 SignatureCustomAppearance.IsForegroundImage 控制層級。

import groupdocs.signature as gs
import groupdocs.signature.options as gso

signature_image_path = "signature.png"
certificate_path      = "JohnSmithCertificate.pfx"

input_pdf  = "SampleDocument.pdf"
output_pdf = "SignedDocument.pdf"

with gs.Signature(input_pdf) as signature:
    sign_options = gso.DigitalSignOptions(certificate_path)
    sign_options.password = "1234567890"
    sign_options.reason   = "Document approval"
    sign_options.contact  = "John Smith"
    sign_options.location = "Head Office"

    # Visible signature placement
    sign_options.visible = True
    sign_options.left    = 350
    sign_options.top     = 100
    sign_options.width   = 200
    sign_options.height  = 70
    sign_options.image_file_path = signature_image_path

    appearance = gso.PdfDigitalSignatureAppearance()
    appearance.foreground = gs.Color.from_argb(50, gs.Color.brown)
    appearance.font_family_name = "Times New Roman"
    appearance.font_size = 12
    appearance.background = gs.Color.from_argb(50, gs.Color.light_gray)
    appearance.is_foreground_image = True   # image on top of text

    sign_options.appearance = appearance

    sign_result = signature.sign(output_pdf, sign_options)

    print(f"\nDocument signed successfully with {len(sign_result.succeeded)} signature(s).")
    print(f"Signed file saved at: {output_pdf}")

7. Security hardening – removal of insecure algorithms

RC2、DES、TripleDES 以及弱 AES 模式已從加密堆疊中移除。僅保留現代、符合 NIST 標準的演算法，提升簽署文件的預設安全等級。

8. LINQ‑style query optimization

簽章 search 與 verify 現在接受 謂詞函式，可在執行繁重的處理步驟之前先過濾簽章，從而降低記憶體使用量並加快批次作業速度。

Search with a predicate

import groupdocs.signature as gs
import groupdocs.signature.options as gso
import groupdocs.signature.domain as gsd

with gs.Signature("document.pdf") as signature:
    search_options = [gso.TextSearchOptions()]

    # Keep only text signatures that contain the word "Approved"
    result = signature.search(search_options,
        lambda sig: isinstance(sig, gsd.TextSignature) and "Approved" in sig.text)

    for sig in result.signatures:
        print(f"Found: {sig.text}")

Verify with a predicate

with gs.Signature("signed_document.pdf") as signature:
    verify_options = gso.TextVerifyOptions("John Smith")

    # Verify only signatures on page 1
    result = signature.verify(verify_options,
        lambda sig: sig.page_number == 1)

    print(f"Found {len(result)} verified signatures on page 1")

9. Fixed Linux DOC preview crash

GeneratePreview() 在 Linux 上處理 Microsoft Word（.doc）檔案時不再拋出 TypeInitializerException，恢復跨平台預覽功能。

Upgrade instructions

pip install --upgrade groupdocs-signature-net

Note: The package name groupdocs-signature-net is used for the Python‑via‑.NET wrapper.

Resources

持續關注即將發布的版本，並留意官方部落格以取得效能技巧與最佳實踐指南。