Here is a Regular Expression to get the source value of an image tag regardless of the location of the src attribute.

(?<=img\s+[^>]*src\=[\x27\x22])[^\x27\x22]*(?=[\x27\x22])

Options: case insensitive

Assert that the regex below can be matched, with the match ending at this position (positive lookbehind) «(?<=img\s+[^>]*src\=[\x27\x22])»
- Match the characters “img” literally «img»
- Match a single character that is a “whitespace character” (spaces, tabs, line breaks, etc.) «\s+»
  - Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
- Match any character that is NOT a “>” «[^>]*»
  - Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
- Match the characters “src” literally «src»
- Match the character “=” literally «\=»
- Match a single character present in the list below «[\x27\x22]»
- ASCII character 0×27 (39 decimal) «\x27»
- ASCII character 0×22 (34 decimal) «\x22»
Match a single character NOT present in the list below «[^\x27\x22]*»
- Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
- ASCII character 0×27 (39 decimal) «\x27»
- ASCII character 0×22 (34 decimal) «\x22»
Assert that the regex below can be matched, starting at this position (positive lookahead) «(?=[\x27\x22])»
- Match a single character present in the list below «[\x27\x22]»
  - ASCII character 0×27 (39 decimal) «\x27»
  - ASCII character 0×22 (34 decimal) «\x22»

Created with RegexBuddy

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Regular Expression for Image Source