imglab 0.2.0
Official Python library to integrate with imglab services.
License: MIT License
Requires Python: >=3.6

# imglab

`imglab` is the official Python package to integrate with imglab services.

## Installation

```sh
$ pip install imglab
```

## Python compatibility

`imglab` has been successfully tested with the following Python versions: `3.11`, `3.10`, `3.9`, `3.8`, `3.7`, `3.6`.

## Generating URLs

You can use `imglab.url` function to generate imglab compatible URLs for your application.

The easiest way to generate a URL is to specify the name of the `source`, a `path` and required `parameters`:

```python
>>> import imglab
>>> imglab.url("assets", "image.jpeg", width=500, height=600)
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600'

>>> imglab.url("avatars", "user-01.jpeg", width=300, height=300, mode="crop", crop="face", format="webp")
'https://avatars.imglab-cdn.net/user-01.jpeg?width=300&height=300&mode=crop&crop=face&format=webp'

```

If some specific settings are required for the source you can use an instance of `imglab.Source` class instead:

```python
>>> imglab.url(imglab.Source("assets"), "image.jpeg", width=500, height=600)
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600'

```

### Using secure image sources

For sources that require signed URLs you can specify `secure_key` and `secure_salt` attributes:

```python
>>> source = imglab.Source("assets", secure_key="55IX1RVlDHpgl/4D", secure_salt="ITvYA2lPfyz0w8/v")
>>> imglab.url(source, "image.jpeg", width=500, height=600)
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&signature=16sKGTU_dgMVqzU1JUBfkkmUV3vCKoZFkwVBYiqnGZU'

```

`signature` query parameter will be automatically generated and attached to the returned URL.

> Note: `secure_key` and `secure_salt` attributes are secrets that should not be added to a code repository. Please use environment vars or other secure method to use them in your application.

### Using HTTP instead of HTTPS

In the case that HTTP schema is required instead of HTTPS you can set `https` attribute to `False` when creating the source:

```python
>>> imglab.url(imglab.Source("assets", https=False), "image.jpeg", width=500, height=600)
'http://assets.imglab-cdn.net/image.jpeg?width=500&height=600'

```

> Note: HTTPS is the default and recommended way to generate URLs with imglab.

### Specifying parameters

Any parameter from the imglab API can be used to generate URLs with `imglab.url` method. For parameters that required dashes characters like `trim-color` you can use regular underscore argument names like `trim_color` those will be normalized in the URL generation to it's correct form:

```python
>>> imglab.url("assets", "image.jpeg", trim="color", trim_color="black")
'https://assets.imglab-cdn.net/image.jpeg?trim=color&trim-color=black'

```

If necessary you can pass a dictionary instead of a list of keyword arguments, unpacking the dictionary with `**` operator:

```python
>>> imglab.url("assets", "image.jpeg", **{"trim": "color", "trim-color": "black"})
'https://assets.imglab-cdn.net/image.jpeg?trim=color&trim-color=black'

```

### Specifying color parameters

Some imglab parameters can receive a color as value. It is possible to specify these color values as strings:

```python
>>> # Specifying a RGB color as string
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color="255,0,0")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=255%2C0%2C0'

>>> # Specifying a RGBA color as string
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color="255,0,0,128")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=255%2C0%2C0%2C128'

>>> # Specifying a named color as string
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color="red")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=red'

>>> # Specifying a hexadecimal color as string
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color="F00")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=F00'

```

You can additionally use `imglab.color` helper to specify color values:

```python
>>> from imglab import color

>>> # Using color helper function for a RGB color
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color=color(255, 0, 0))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=255%2C0%2C0'

>>> # Using color helper function for a RGBA color
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color=color(255, 0, 0, 128))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=255%2C0%2C0%2C128'

>>> # Using color helper function for a named color
>>> imglab.url("assets", "image.jpeg", width=500, height=600, mode="contain", background_color=color("red"))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&mode=contain&background-color=red'

```

> Note: specify hexadecimal color values using `imglab.color` helper function is not allowed. You can use strings instead.

### Specifying position parameters

Some imglab parameters can receive a position as value. It is possible to specify these values using strings:

```python
>>> # Specifying a horizontal and vertical position as string
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop="left,top")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=left%2Ctop'

>>> # Specifying a vertical and horizontal position as string
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop="top,left")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=top%2Cleft'

>>> # Specifying a position as string
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop="left")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=left'

```

You can additionally use `imglab.position` helper function to specify position values:

```python
>>> from imglab import position

>>> # Using position function helper for a horizontal and vertical position
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop=position("left", "top"))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=left%2Ctop'

>>> # Using position function helper for a vertical and horizontal position
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop=position("top", "left"))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=top%2Cleft'

>>> # Using position function helper for a single position
>>> imglab.url("assets", "image.jpeg", width=500, height=500, mode="crop", crop=position("left"))
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=500&mode=crop&crop=left'

```

### Specifying URL parameters

Some imglab parameters can receive URLs as values. It is possible to specify these parameter values as strings:

```python
>>> imglab.url("assets", "image.jpeg", width=500, height=600, watermark="logo.svg")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&watermark=logo.svg'

```

And even use parameters if required:

```python
>>> imglab.url("assets", "image.jpeg", width=500, height=600, watermark="logo.svg?width=100&format=png")
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&watermark=logo.svg%3Fwidth%3D100%26format%3Dpng'

```

Additionally you can use nested `imglab.url` calls to specify these URL values:

```python
>>> imglab.url(
...     "assets",
...     "image.jpeg",
...     width=500,
...     height=600,
...     watermark=imglab.url("assets", "logo.svg", width=100, format="png")
... )
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&watermark=https%3A%2F%2Fassets.imglab-cdn.net%2Flogo.svg%3Fwidth%3D100%26format%3Dpng'

```

If the resource is located in a different source we can specify it using `imglab.url`:

```python
>>> imglab.url(
...     "assets",
...     "image.jpeg",
...     width=500,
...     height=600,
...     watermark=imglab.url("marketing", "logo.svg", width=100, format="png")
... )
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&watermark=https%3A%2F%2Fmarketing.imglab-cdn.net%2Flogo.svg%3Fwidth%3D100%26format%3Dpng'

```

Using secure sources for URLs parameter values is possible too:

```python
>>> marketing = imglab.Source("marketing", secure_key="55IX1RVlDHpgl/4D", secure_salt="ITvYA2lPfyz0w8/v")
>>> imglab.url(
...     "assets",
...     "image.jpeg",
...     width=500,
...     height=600,
...     watermark=imglab.url(marketing, "logo.svg", width=100, format="png")
... )
'https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&watermark=https%3A%2F%2Fmarketing.imglab-cdn.net%2Flogo.svg%3Fwidth%3D100%26format%3Dpng%26signature%3DMd4V23DOkn5hHw_nAjkEG9lKHOZ8wjDBmYi2d5TCaCc'

```

`signature` query parameter will be automatically generated and attached to the nested URL value.

### Specifying URLs with expiration timestamp

The `expires` parameter allows you to specify a UNIX timestamp in seconds after which the request is expired.

If a `datetime` or `struct_time` instance is specified as value to `expires` parameter it will be automatically converted to UNIX timestamp. In the following example, we specify an expiration time of one hour:

```python
import datetime
expires_at = datetime.datetime.utcnow() + datetime.timedelta(hours=1)
imglab.url("assets", "image.jpeg", width=500, expires=expires_at)
```

> Note: The `expires` parameter should be used in conjunction with secure sources. Otherwise, `expires` value could be tampered with.

## Generating URLs for on-premises imglab server

For on-premises imglab server is possible to define custom sources pointing to your server location.

* `https` - a `boolean` value specifying if the source should use https or not (default: `True`)
* `host` - a `string` specifying the host where the imglab server is located. (default: `"imglab-cdn.net"`)
* `port` - an `integer` specifying a port where the imglab server is located. (default: `None`)
* `subdomains` - a `bool` value specifying if the source should be specified using subdomains instead of using the path. (default: `True`)

If we have our on-premises imglab server at `http://my-company.com:8080` with a source named `images` we can use the following source settings to access a `logo.png` image:

```python
>>> source = imglab.Source("images", https=False, host="my-company.com", port=8080)
>>> imglab.url(source, "logo.png", width=300, height=300, format="png")
'http://images.my-company.com:8080/logo.png?width=300&height=300&format=png'

```

It is possible to use secure sources too:

```python
>>> source = imglab.Source(
...     "images",
...     https=False,
...     host="my-company.com",
...     port=8080,
...     secure_key="55IX1RVlDHpgl/4D",
...     secure_salt="ITvYA2lPfyz0w8/v"
... )
>>> imglab.url(source, "logo.png", width=300, height=300, format="png")
'http://images.my-company.com:8080/logo.png?width=300&height=300&format=png&signature=spnbiXwImfp6PpihAqVJenm0IGdC-h5inIhViYp4_TU'

```

### Using sources with disabled subdomains

In the case that your on-premises imglab server is configured to use source names as paths instead of subdomains you can set `subdomains` attribute to `False`:

```python
>>> source = imglab.Source(
...     "images",
...     https=False,
...     host="my-company.com",
...     port=8080,
...     subdomains=False
... )
>>> imglab.url(source, "logo.png", width=300, height=300, format="png")
'http://my-company.com:8080/images/logo.png?width=300&height=300&format=png'

```

## Generating srcsets

You can use `imglab.srcset` function to generate custom string values for `srcset` attributes, to be used for Web responsive images inside an `<img>` HTML element or picture `<source>`.

This function works similarly to function `imglab.url`, expecting the same parameters and values, except for some specific query parameters that have a special meaning and can receive `range` and `list` as values.

> To learn more about responsive images and the `srcset` attribute, you can take a look to the [MDN article about responsive images](https://developer.mozilla.org/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images).

### Fixed size

When enough information is provided about the image output size (using `width` or `height` parameters), `imglab.srcset` function will generate URLs with a default sequence of device pixel ratios.

For the following example we are specying a fixed value of `500` pixels for `width` parameter:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500)
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=1 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=2 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=3 3x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=4 4x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=5 5x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=6 6x

```

A very common practice consists in reducing the quality of images with high pixel density, decreasing the final file size. To achieve this you can optionally specify a `range` object for `quality` parameter, gradually reducing the quality and file size while increasing the image size.

In this example we are specifying a fixed `width` value of `500` pixels and a `quality` range between `80` and `40`:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500, quality=range(80, 40))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=80&dpr=1 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=70&dpr=2 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=61&dpr=3 3x,
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=53&dpr=4 4x,
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=46&dpr=5 5x,
https://assets.imglab-cdn.net/image.jpeg?width=500&quality=40&dpr=6 6x

```

A custom `range` value can be set for `dpr` parameter too, overriding the default sequence of generated dprs:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500, dpr=range(1, 4))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=1 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=2 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=3 3x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=4 4x

```

Using `range` values for `dpr` and `quality` parameters in the same `srcset` call is also possible:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500, dpr=range(1, 4), quality=range(80, 40))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=1&quality=80 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=2&quality=63 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=3&quality=50 3x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=4&quality=40 4x

```

If necessary you can also use a list with explicit values for `dpr` and `quality`:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500, dpr=[1, 2, 3], quality=[80, 75, 60])
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=1&quality=80 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=2&quality=75 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=3&quality=60 3x

```

Or even use a specific `quality` value for all the URLs in the same srcset:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=500, dpr=[1, 2, 3], quality=70)
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=1&quality=70 1x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=2&quality=70 2x,
https://assets.imglab-cdn.net/image.jpeg?width=500&dpr=3&quality=70 3x

```

### Fluid width

When a specific sequence of width values are required you can use `range`, `imglab.sequence`, or `list` values for `width` parameter.

When a `range` value is used, a `imglab.sequence` with a default size of 16 URLs will be generated inside the specified interval:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=range(100, 2000))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100 100w,
https://assets.imglab-cdn.net/image.jpeg?width=122 122w,
https://assets.imglab-cdn.net/image.jpeg?width=149 149w,
https://assets.imglab-cdn.net/image.jpeg?width=182 182w,
https://assets.imglab-cdn.net/image.jpeg?width=222 222w,
https://assets.imglab-cdn.net/image.jpeg?width=271 271w,
https://assets.imglab-cdn.net/image.jpeg?width=331 331w,
https://assets.imglab-cdn.net/image.jpeg?width=405 405w,
https://assets.imglab-cdn.net/image.jpeg?width=494 494w,
https://assets.imglab-cdn.net/image.jpeg?width=603 603w,
https://assets.imglab-cdn.net/image.jpeg?width=737 737w,
https://assets.imglab-cdn.net/image.jpeg?width=900 900w,
https://assets.imglab-cdn.net/image.jpeg?width=1099 1099w,
https://assets.imglab-cdn.net/image.jpeg?width=1341 1341w,
https://assets.imglab-cdn.net/image.jpeg?width=1638 1638w,
https://assets.imglab-cdn.net/image.jpeg?width=2000 2000w

```

If required you can specify a `range` value for `quality` parameter too:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=range(100, 2000), quality=range(80, 40))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100&quality=80 100w,
https://assets.imglab-cdn.net/image.jpeg?width=122&quality=76 122w,
https://assets.imglab-cdn.net/image.jpeg?width=149&quality=73 149w,
https://assets.imglab-cdn.net/image.jpeg?width=182&quality=70 182w,
https://assets.imglab-cdn.net/image.jpeg?width=222&quality=66 222w,
https://assets.imglab-cdn.net/image.jpeg?width=271&quality=63 271w,
https://assets.imglab-cdn.net/image.jpeg?width=331&quality=61 331w,
https://assets.imglab-cdn.net/image.jpeg?width=405&quality=58 405w,
https://assets.imglab-cdn.net/image.jpeg?width=494&quality=55 494w,
https://assets.imglab-cdn.net/image.jpeg?width=603&quality=53 603w,
https://assets.imglab-cdn.net/image.jpeg?width=737&quality=50 737w,
https://assets.imglab-cdn.net/image.jpeg?width=900&quality=48 900w,
https://assets.imglab-cdn.net/image.jpeg?width=1099&quality=46 1099w,
https://assets.imglab-cdn.net/image.jpeg?width=1341&quality=44 1341w,
https://assets.imglab-cdn.net/image.jpeg?width=1638&quality=42 1638w,
https://assets.imglab-cdn.net/image.jpeg?width=2000&quality=40 2000w

```

If you want to generate a sequence of numbers for `width` parameter with a specific number of URLs you can use `imglab.sequence` function helper:

```python
# You can import the function helper if necessary
>>> from imglab import sequence

# Generating a srcset string with a sequence of 5 URLs between 100 and 2000 pixels for width parameter
>>> srcset = imglab.srcset("assets", "image.jpeg", width=sequence(100, 2000, 5))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100 100w,
https://assets.imglab-cdn.net/image.jpeg?width=211 211w,
https://assets.imglab-cdn.net/image.jpeg?width=447 447w,
https://assets.imglab-cdn.net/image.jpeg?width=946 946w,
https://assets.imglab-cdn.net/image.jpeg?width=2000 2000w

```

Using a list with specific values will generate URLs only for those widths:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=[100, 300, 500])
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100 100w,
https://assets.imglab-cdn.net/image.jpeg?width=300 300w,
https://assets.imglab-cdn.net/image.jpeg?width=500 500w

```

It is also possible to specify a list of values for `height` and `quality` parameters:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=[100, 300, 500], height=[200, 400, 600], quality=[75, 70, 65])
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100&height=200&quality=75 100w,
https://assets.imglab-cdn.net/image.jpeg?width=300&height=400&quality=70 300w,
https://assets.imglab-cdn.net/image.jpeg?width=500&height=600&quality=65 500w

```

### No size

When `srcset` function doesn't have information about the image output size (`width` or `height` parameters are not set) it will generate a default `imglab.sequence` of 16 URLs specifying a `width` value with an interval between `100` and `8192` pixels:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg")
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100 100w,
https://assets.imglab-cdn.net/image.jpeg?width=134 134w,
https://assets.imglab-cdn.net/image.jpeg?width=180 180w,
https://assets.imglab-cdn.net/image.jpeg?width=241 241w,
https://assets.imglab-cdn.net/image.jpeg?width=324 324w,
https://assets.imglab-cdn.net/image.jpeg?width=434 434w,
https://assets.imglab-cdn.net/image.jpeg?width=583 583w,
https://assets.imglab-cdn.net/image.jpeg?width=781 781w,
https://assets.imglab-cdn.net/image.jpeg?width=1048 1048w,
https://assets.imglab-cdn.net/image.jpeg?width=1406 1406w,
https://assets.imglab-cdn.net/image.jpeg?width=1886 1886w,
https://assets.imglab-cdn.net/image.jpeg?width=2530 2530w,
https://assets.imglab-cdn.net/image.jpeg?width=3394 3394w,
https://assets.imglab-cdn.net/image.jpeg?width=4553 4553w,
https://assets.imglab-cdn.net/image.jpeg?width=6107 6107w,
https://assets.imglab-cdn.net/image.jpeg?width=8192 8192w

```

It is always possible to change this default behavior using `imglab.sequence` function helper. In the following example we are specifying a sequence of 10 different URLs between `320` and `4096` pixels:

```python
>>> from imglab import sequence

>>> srcset = imglab.srcset("assets", "image.jpeg", width=sequence(320, 4096, 10))
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=320 320w,
https://assets.imglab-cdn.net/image.jpeg?width=425 425w,
https://assets.imglab-cdn.net/image.jpeg?width=564 564w,
https://assets.imglab-cdn.net/image.jpeg?width=749 749w,
https://assets.imglab-cdn.net/image.jpeg?width=994 994w,
https://assets.imglab-cdn.net/image.jpeg?width=1319 1319w,
https://assets.imglab-cdn.net/image.jpeg?width=1751 1751w,
https://assets.imglab-cdn.net/image.jpeg?width=2324 2324w,
https://assets.imglab-cdn.net/image.jpeg?width=3086 3086w,
https://assets.imglab-cdn.net/image.jpeg?width=4096 4096w

```

### Image aspect ratio and srcset

A usual scenario is to generate multiple URLs while maintaining the same aspect ratio for all of them. If a specific image aspect ratio is required while using `srcset` function you can set a value to `aspect-ratio` parameter along with `mode` parameter using  `crop`, `contain`, `face`, or `force` resize modes.

For the following example we are using a specific value of  `300` pixels for `width`, and an aspect ratio of `1:1` (square), cropping the image with `crop` resize mode and setting output format to `webp`:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=300, aspect_ratio="1:1", mode="crop", format="webp")
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=1 1x,
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=2 2x,
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=3 3x,
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=4 4x,
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=5 5x,
https://assets.imglab-cdn.net/image.jpeg?width=300&aspect-ratio=1%3A1&mode=crop&format=webp&dpr=6 6x

```

You can instead use `height` value. In this example we are specifying a fixed value of `300` pixels for `height` parameter, a `aspect-ratio` of `16:9` (widescreen) with `crop` resize mode, and `webp` output format:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", height=300, aspect_ratio="16:9", mode="crop", format="webp")
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=1 1x,
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=2 2x,
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=3 3x,
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=4 4x,
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=5 5x,
https://assets.imglab-cdn.net/image.jpeg?height=300&aspect-ratio=16%3A9&mode=crop&format=webp&dpr=6 6x

```

You can also use fluid values for `width` parameter while maintaining the same aspect ratio for all generated URLs. In this example, we are using a `range` value between `100` and `4096` for `width` parameter, a value of `1:1` for `aspect-ratio`, `crop` resize mode and `webp` output format:

```python
>>> srcset = imglab.srcset("assets", "image.jpeg", width=range(100, 4096), aspect_ratio="1:1", mode="crop", format="webp")
>>> print(srcset)
https://assets.imglab-cdn.net/image.jpeg?width=100&aspect-ratio=1%3A1&mode=crop&format=webp 100w,
https://assets.imglab-cdn.net/image.jpeg?width=128&aspect-ratio=1%3A1&mode=crop&format=webp 128w,
https://assets.imglab-cdn.net/image.jpeg?width=164&aspect-ratio=1%3A1&mode=crop&format=webp 164w,
https://assets.imglab-cdn.net/image.jpeg?width=210&aspect-ratio=1%3A1&mode=crop&format=webp 210w,
https://assets.imglab-cdn.net/image.jpeg?width=269&aspect-ratio=1%3A1&mode=crop&format=webp 269w,
https://assets.imglab-cdn.net/image.jpeg?width=345&aspect-ratio=1%3A1&mode=crop&format=webp 345w,
https://assets.imglab-cdn.net/image.jpeg?width=442&aspect-ratio=1%3A1&mode=crop&format=webp 442w,
https://assets.imglab-cdn.net/image.jpeg?width=566&aspect-ratio=1%3A1&mode=crop&format=webp 566w,
https://assets.imglab-cdn.net/image.jpeg?width=724&aspect-ratio=1%3A1&mode=crop&format=webp 724w,
https://assets.imglab-cdn.net/image.jpeg?width=928&aspect-ratio=1%3A1&mode=crop&format=webp 928w,
https://assets.imglab-cdn.net/image.jpeg?width=1188&aspect-ratio=1%3A1&mode=crop&format=webp 1188w,
https://assets.imglab-cdn.net/image.jpeg?width=1522&aspect-ratio=1%3A1&mode=crop&format=webp 1522w,
https://assets.imglab-cdn.net/image.jpeg?width=1949&aspect-ratio=1%3A1&mode=crop&format=webp 1949w,
https://assets.imglab-cdn.net/image.jpeg?width=2497&aspect-ratio=1%3A1&mode=crop&format=webp 2497w,
https://assets.imglab-cdn.net/image.jpeg?width=3198&aspect-ratio=1%3A1&mode=crop&format=webp 3198w,
https://assets.imglab-cdn.net/image.jpeg?width=4096&aspect-ratio=1%3A1&mode=crop&format=webp 4096w

```

## License

imglab source code is released under [MIT License](LICENSE).