title: process_image
---
module: lektor.imagetools
---
signature: ctx, source_image, dst_filename, width, height=None
---
summary: Build an image from a source image, optionally compressing and resizing.
---
type: function
---
version_added: 2.0
---
body:

This function takes a [Context :ref](../../build/context/) object, the absolute paths to the image's source and target files, and the target image's width. If height is `None`, it is calculated from the source image width and the target width so that the image is scaled proportionally.

Used internally for the implementation of [thumbnail :ref](../../db/record/thumbnail), and exposed as an API for image-processing plugins.

## Example

```python
from lektor.build_programs import AttachmentBuildProgram
from lektor.context import get_ctx
from lektor.db import Image
from lektor.imagetools import process_image
from lektor.pluginsystem import Plugin


class ResizeBuildProgram(AttachmentBuildProgram):
    def build_artifact(self, artifact):
        ctx = get_ctx()
        width = 1024
        source_img = artifact.source_obj.attachment_filename
        artifact.ensure_dir()

        process_image(ctx,
                      source_img,
                      artifact.dst_filename,
                      width)


class ImageResizePlugin(Plugin):
    def on_setup_env(self, **extra):
        self.env.add_build_program(Image, ResizeBuildProgram)
```