GolfScript, 13 bytes

{48-}/]10base

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{   }/          # For each byte in the input
 48-            # Subtract 48
      ]         # Put all results in an array
       10base   # Convert to base 10

Alternative 13 byte solution:

0\{48-\10*+}/

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0\              # Put 0 under the input
  {        }/   # For each byte in the input
   48-          # Subtract 48
      \10*      # Multiply the output by 10
          +     # Add the subtracted ASCII

GolfScript, 13 12 bytes

{48-}%10base

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{   }%         # For each byte in the input
 48-           # Subtract 48
      10base   # Convert to base 10