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 |