# Kotlin - HTML to Image Example

Generate PNG, JPG, WebP, and PDF output with Kotlin, using HTML/CSS or reusable templates rendered in Google Chrome.

## Generating images with Kotlin

1.  Send your HTML/CSS to the API.
2.  The API renders it in Google Chrome.
3.  Read the generated image URL from the JSON response.

See [Creating an image](/getting-started/using-the-api/#creating-an-image) for request parameters. A response includes the image's `url` and `id`.

![Example image generated from HTML with Kotlin](/assets/images/dog-rates-example.png)

## Authentication with Kotlin

Use HTTP Basic authentication with your API ID as the username and API key as the password. Find both in the [dashboard](https://htmlcsstoimage.com/dashboard). Keep credentials in server-side configuration or environment variables.

## Kotlin example code

The example sends a POST request to `https://hcti.io/v1/image`. Image creation requires `images:create`. See [authentication and API keys](/getting-started/using-the-api/api-keys/) for scoped credentials and access errors.

This example uses the built-in Java 11+ `HttpClient` from Kotlin and [`kotlinx.serialization`](https://github.com/Kotlin/kotlinx.serialization) to encode the JSON request body.

Add the JSON serialization dependency:

```kotlin
dependencies {
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.7.3")
}
```

```kotlin
import kotlinx.serialization.encodeToString
import kotlinx.serialization.json.Json
import java.net.URI
import java.net.http.HttpClient
import java.net.http.HttpRequest
import java.net.http.HttpResponse
import java.nio.charset.StandardCharsets
import java.util.Base64


fun main() {
    val userId = "your-user-id"
    val apiKey = "your-api-key"


    val payload = mapOf(
        "html" to "<div class='box'>Kotlin ✅</div>",
        "css" to ".box { border: 4px solid #03B875; padding: 20px; font-family: Roboto, sans-serif; }",
        "google_fonts" to "Roboto"
    )
    val body = Json.encodeToString(payload)


    val auth = Base64.getEncoder().encodeToString(
        "$userId:$apiKey".toByteArray(StandardCharsets.UTF_8)
    )


    val request = HttpRequest.newBuilder()
        .uri(URI.create("https://hcti.io/v1/image"))
        .header("Authorization", "Basic $auth")
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(body))
        .build()


    val response = HttpClient.newHttpClient()
        .send(request, HttpResponse.BodyHandlers.ofString())


    if (response.statusCode() !in 200..299) {
        error("Request failed: ${response.statusCode()} ${response.body()}")
    }


    println(response.body())
    // {"url":"https://hcti.io/v1/image/1113184e-419f-49f1-b231-2069942a186f"}
}
```

## Need help?

Talk to a human. Email [support@htmlcsstoimage.com](mailto:support@htmlcsstoimage.com) and we’ll help you get started.