title: Obtain text fields from a png file
body: <p>Nothing seems to work so far. I got to see with <a href="http://manpages.ubuntu.com/manpages/precise/man1/pnginfo.1.html" rel="nofollow noreferrer">pnginfo</a> the following message:</p>
  
  <pre><code>concept_Sjet_dream6.png...
    Image Width: 200 Image Length: 240
    Bitdepth (Bits/Sample): 8
    Channels (Samples/Pixel): 2
    Pixel depth (Pixel Depth): 16
    Colour Type (Photometric Interpretation): GRAYSCALE with alpha channel 
    Image filter: Single row per byte filter 
    Interlacing: No interlacing 
    Compression Scheme: Deflate method 8, 32k window
    Resolution: 11811, 11811 (pixels per meter)
    FillOrder: msb-to-lsb
    Byte Order: Network (Big Endian)
    Number of text strings: 1 of 9
      Comment (xTXt deflate compressed): The comment
  </code></pre>
  
  <p>But the remaining text strings are missing. I did also try other solutions in <a href="https://stackoverflow.com/questions/2190236/how-can-i-read-png-metadata-from-php">stackoverflow</a>, they didn't work either. pngchunks provides this information:</p>
  
  <pre><code>Chunk: Data Length 13 (max 2147483647), Type 1380206665 [IHDR]
    Critical, public, PNG 1.2 compliant, unsafe to copy
    IHDR Width: 200
    IHDR Height: 240
    IHDR Bitdepth: 8
    IHDR Colortype: 4
    IHDR Compression: 0
    IHDR Filter: 0
    IHDR Interlace: 0
    IHDR Compression algorithm is Deflate
    IHDR Filter method is type zero (None, Sub, Up, Average, Paeth)
    IHDR Interlacing is disabled
    Chunk CRC: -277290027
  Chunk: Data Length 1 (max 2147483647), Type 1111970419 [sRGB]
    Ancillary, public, PNG 1.2 compliant, unsafe to copy
    ... Unknown chunk type
    Chunk CRC: -1362223895
  Chunk: Data Length 2 (max 2147483647), Type 1145523042 [bKGD]
    Ancillary, public, PNG 1.2 compliant, unsafe to copy
    ... Unknown chunk type
    Chunk CRC: -2020619073
  Chunk: Data Length 9 (max 2147483647), Type 1935231088 [pHYs]
    Ancillary, public, PNG 1.2 compliant, safe to copy
    ... Unknown chunk type
    Chunk CRC: 2024095606
  Chunk: Data Length 7 (max 2147483647), Type 1162692980 [tIME]
    Ancillary, public, PNG 1.2 compliant, unsafe to copy
    ... Unknown chunk type
    Chunk CRC: 292503155
  Chunk: Data Length 19 (max 2147483647), Type 1951942004 [tEXt]
    Ancillary, public, PNG 1.2 compliant, safe to copy
    ... Unknown chunk type
    Chunk CRC: -528748773
  Chunk: Data Length 8192 (max 2147483647), Type 1413563465 [IDAT]
    Critical, public, PNG 1.2 compliant, unsafe to copy
    IDAT contains image data
    Chunk CRC: -309524018
  Chunk: Data Length 8192 (max 2147483647), Type 1413563465 [IDAT]
    Critical, public, PNG 1.2 compliant, unsafe to copy
    IDAT contains image data
    Chunk CRC: -1646200198
  Chunk: Data Length 2301 (max 2147483647), Type 1413563465 [IDAT]
    Critical, public, PNG 1.2 compliant, unsafe to copy
    IDAT contains image data
    Chunk CRC: -810299134
  Chunk: Data Length 0 (max 2147483647), Type 1145980233 [IEND]
    Critical, public, PNG 1.2 compliant, unsafe to copy
    IEND contains no data
    Chunk CRC: -1371381630
  </code></pre>
  
  <p>Sample image:</p>
  
  <p><img src="https://i.stack.imgur.com/zYfli.png" alt="sample image for this problem"></p>
  
  <p>I'm very confused. Thank you anyone.</p>
  
  <p>PD: apparently this happens with every image, this is not a special case but the usual case.</p>