Skip to content

Sain (サイン)

A Compose Multiplatform library for capturing and exporting signatures as ImageBitmap with customizable options. Perfect for electronic signature, legal documents and more.


Including it in your project:

Add the Maven Central repository if it is not already there:

repositories {
    mavenCentral()
}

In multiplatform projects, add a dependency to the commonMain source set dependencies

kotlin {
    sourceSets {
        commonMain {
             dependencies {
                 implementation("io.github.joelkanyi:sain:<latest-version>")
             }
        }
    }
}

In Android projects, add the dependency to your dependencies block in your app's build.gradle file:

dependencies {
    implementation("io.github.joelkanyi:sain:<latest-version>")
}

For those using Gradle Version Catalog, you can add the dependency as follows:

[versions]
sain = "<latest-version>"

[libraries]
sain = { module = "io.github.joelkanyi:sain", version.ref = "sain" }

Add then include the dependency in your project as follows:

dependencies {
    implementation(libs.sain)
}

Usage

Add the Sain composable into your project and customize it according to your needs: 

var imageBitmap: ImageBitmap? by remember {
    mutableStateOf(null)
}

Sain(
    signatureHeight = 250.dp,
    signaturePadColor = Color.White,
    signatureBorderStroke = BorderStroke(
        width = .5.dp,
        color = MaterialTheme.colorScheme.onSurface,
    ),
    signaturePadShape = RoundedCornerShape(8.dp),
    onComplete = { signatureBitmap ->
        if (signatureBitmap != null) {
            imageBitmap = signatureBitmap
        } else {
            println("Signature is empty")
        }
    },
) { action ->
    Row(
        modifier = Modifier
            .padding(top = 16.dp)
            .fillMaxWidth(),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
    ) {
        Button(
            modifier = Modifier.weight(1f),
            onClick = {
                imageBitmap = null
                action(SignatureAction.CLEAR)
            },
        ) {
            Text("Clear")
        }
        Button(
            modifier = Modifier.weight(1f),
            onClick = {
                action(SignatureAction.COMPLETE)
            },
        ) {
            Text("Complete")
        }
    }
}


Actions

The Sain composable takes in an actions parameter which is a lambda that takes in a SignatureAction enum. The SignatureAction enum has two values: - CLEAR - Clears the signature - COMPLETE - Completes the signature and returns the signature as an ImageBitmap in the onComplete lambda


Customization

  • signatureColor - The color of the signature
  • signatureThickness - The thickness of the signature
  • signatureHeight: The height of the signature pad.
  • signaturePadColor: The color of the signature pad.
  • signatureBorderStroke: The border stroke of the signature pad.
  • signaturePadShape: The shape of the signature pad.

License

Copyright 2023 Joel Kanyi

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.