12 Apr 2020

Tesseract TSV format

History / Edit / PDF / EPUB / BIB / 5 min read (~871 words)

Tesseract (an open source OCR engine) supports a TSV format as output. I looked online for some documentation about the columns but couldn't find anything, so I looked at the source code.

Here is a summary description of each column, what they represent, and the range of valid values they can have.

  • level: hierarchical layout (a word is in a line, which is in a paragraph, which is in a block, which is in a page), a value from 1 to 5
    • 1: page
    • 2: block
    • 3: paragraph
    • 4: line
    • 5: word
  • page_num: when provided with a list of images, indicates the number of the file, when provided with a multi-pages document, indicates the page number, starting from 1
  • block_num: block number within the page, starting from 0
  • par_num: paragraph number within the block, starting from 0
  • line_num: line number within the paragraph, starting from 0
  • word_num: word number within the line, starting from 0
  • left: x coordinate in pixels of the text bounding box top left corner, starting from the left of the image
  • top: y coordinate in pixels of the text bounding box top left corner, starting from the top of the image
  • width: width of the text bounding box in pixels
  • height: height of the text bounding box in pixels
  • conf: confidence value, from 0 (no confidence) to 100 (maximum confidence), -1 for all level except 5
  • text: detected text, empty for all levels except 5

Here is an example of the TSV format output, for reference.

level page_num block_num par_num line_num word_num left top width height conf text
1 1 0 0 0 0 0 0 1024 800 -1
2 1 1 0 0 0 98 66 821 596 -1
3 1 1 1 0 0 98 66 821 596 -1
4 1 1 1 1 0 105 66 719 48 -1
5 1 1 1 1 1 105 66 74 32 90 The
5 1 1 1 1 2 205 67 143 40 87 (quick)
5 1 1 1 1 3 376 69 153 41 89 [brown]
5 1 1 1 1 4 559 71 105 40 89 {fox}
5 1 1 1 1 5 687 73 137 41 89 jumps!
4 1 1 1 2 0 104 115 784 51 -
5 1 1 1 2 1 104 115 96 33 91 Over
5 1 1 1 2 2 224 117 60 32 89 the
5 1 1 1 2 3 310 117 224 39 88 $43,456.78
5 1 1 1 2 4 561 121 136 42 92 <lazy>
5 1 1 1 2 5 722 123 70 32 92 #90
5 1 1 1 2 6 818 125 70 41 89 dog