#  `delete_blank`

Delete blank or near-blank pages
## Usage
> pdftl `<input>` `delete_blank` `'[spec](params)'` `output` `<output>`

## Details
The `delete_blank` operation removes pages that are blank or visually uniform
by rendering each candidate page at low resolution and analysing its pixels.

**Detection methods:**

Two complementary methods are available. If both are specified, a page must
satisfy *both* criteria to be deleted.

- **`threshold`** — ink coverage: the fraction of pixels that differ from
  pure white (0.0–1.0, default `0.005`). Use `threshold=0` for
  pure-white-only detection.

- **`stddev`** — pixel standard deviation: how uniform the page is regardless
  of its base colour. A solid white *or* solid coloured page both score near
  zero (default `5.0`, on a 0–255 scale). Useful for detecting pages with
  coloured backgrounds.

- **`mode`** — colour space for analysis: `grey` (default) or `rgb`.
  `rgb` is more accurate for coloured backgrounds; `grey` is faster.

If neither `threshold` nor `stddev` is specified, both defaults are applied.

**DPI:**

The `dpi` parameter controls the render resolution used for detection
(default: `30`). Higher values catch finer marks but are slower.

**Selector:**

An optional page selector (e.g. `1-5`, `odd`) restricts which pages are
*candidates* for deletion. Non-candidate pages are always kept.

The syntax is `[selector](Key=Value, ...)`, where all parameters are optional.

### Parameters

| Parameter   | Description                                             | Default | Example      |
| :---------- | :------------------------------------------------------ | :------ | :----------- |
| `threshold` | Max ink coverage fraction to consider blank (0.0–1.0)  | `0.005` | `threshold=0` |
| `stddev`    | Max pixel stddev to consider uniform (0–255)            | `5.0`   | `stddev=2.5` |
| `mode`      | Colour space: `grey` or `rgb`                           | `grey`  | `mode=rgb`   |
| `dpi`       | Render resolution for detection                         | `30`    | `dpi=72`     |
## Examples

> Delete blank pages using default threshold and stddev detection.
```
pdftl in.pdf delete_blank output out.pdf
```

> Delete only perfectly white pages (zero ink coverage).
```
pdftl in.pdf delete_blank '(threshold=0)' output out.pdf
```

> Delete pages that are visually uniform in any colour, using RGB analysis.
```
pdftl in.pdf delete_blank '(stddev=3,mode=rgb)' output out.pdf
```

> On even pages only, delete near-blank pages rendered at 72 dpi.
```
pdftl in.pdf delete_blank 'even(threshold=0.01,dpi=72)' output out.pdf
```


**Tags**: in_place, pages, optimization, delete

*Source: pdftl.operations.delete_blank*

*Read online: [https://pdftl.readthedocs.io/en/stable/operations/delete_blank.html](https://pdftl.readthedocs.io/en/stable/operations/delete_blank.html)*

*Type: Operation*