detectImageFormat function

String? detectImageFormat(String? assetPath, Uint8List? imageData)

Detects image format from asset path or image data.

Returns the format string ('png', 'svg', 'jpg', 'jpeg', etc.) based on:

1. File extension from assetPath if provided
2. Image data magic bytes if imageData is provided
3. Returns null if format cannot be determined

Implementation

String? detectImageFormat(String? assetPath, Uint8List? imageData) {
  // First, try to detect from file extension
  if (assetPath != null && assetPath.isNotEmpty) {
    final extension = assetPath.split('.').last.toLowerCase();
    if (extension == 'svg') return 'svg';
    if (extension == 'png') return 'png';
    if (extension == 'jpg' || extension == 'jpeg') return 'jpg';
    if (extension == 'gif') return 'gif';
    if (extension == 'webp') return 'webp';
  }

  // If no extension or format not detected, try to detect from image data magic bytes
  if (imageData != null && imageData.length >= 4) {
    // PNG: 89 50 4E 47 (PNG signature)
    if (imageData[0] == 0x89 &&
        imageData[1] == 0x50 &&
        imageData[2] == 0x4E &&
        imageData[3] == 0x47) {
      return 'png';
    }

    // JPEG: FF D8 FF
    if (imageData[0] == 0xFF &&
        imageData[1] == 0xD8 &&
        imageData[2] == 0xFF) {
      return 'jpg';
    }

    // GIF: 47 49 46 38 (GIF8)
    if (imageData[0] == 0x47 &&
        imageData[1] == 0x49 &&
        imageData[2] == 0x46 &&
        imageData[3] == 0x38) {
      return 'gif';
    }

    // SVG: Check if it starts with '<' or contains 'svg' in the first bytes
    // SVG files are XML, so they typically start with '<' or whitespace followed by '<'
    final firstBytes = String.fromCharCodes(imageData.take(100));
    if (firstBytes.trim().startsWith('<') &&
        (firstBytes.contains('<svg') || firstBytes.contains('SVG'))) {
      return 'svg';
    }
  }

  // Default to PNG if we have image data but can't determine format
  // (PNG is the most common format for icons)
  if (imageData != null) {
    return 'png';
  }

  return null;
}