How to use it¶

Compile from Source Code¶

You will need JDK 11 or newer and a C/C++ toolchain (GCC or MSVC) installed.

git clone https://github.com/manticore-projects/fpng-java.git
cd fpng-java
gradle build

Build Dependencies¶

FPNG-Java (SSE2 encoder, always safe to load):

Maven

<dependency>
    <groupId>com.manticore-projects.tools</groupId>
    <artifactId>fpng-java</artifactId>
    <version>1.4.1</version>
</dependency>

Gradle

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.manticore-projects.tools:fpng-java:1.4.1'
}

FPNGE-Java (AVX2 encoder, only load on supported hardware):

Maven

<dependency>
    <groupId>com.manticore-projects.tools</groupId>
    <artifactId>fpnge-java</artifactId>
    <version>1.4.1</version>
</dependency>

Gradle

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.manticore-projects.tools:fpnge-java:1.4.1'
}

Java Usage¶

Basic Encoding¶

import com.manticore.tools.FPNGEncoder;
import java.awt.image.BufferedImage;

// Encode a BufferedImage to PNG bytes (3 or 4 channels)
byte[] pngBytes = FPNGEncoder.encode(image, 4, 0);

Automatic Encoder Selection (SSE2 vs AVX2)¶

The SSE2 encoder (FPNG) is always safe to load on any x86-64 CPU. The AVX2 encoder (FPNGE) must only be loaded if the CPU supports it — otherwise the native library will crash on load.

Use the hasAVX2() probe from the FPNG library to decide at runtime:

import com.manticore.tools.FPNGEncoder;
import com.manticore.tools.FPNGEEncoder;

// Initialise FPNG (always safe) and probe CPU features
FPNGEncoder.ENCODER.fpng_init();
boolean useAVX2 = FPNGEncoder.ENCODER.hasAVX2() != 0;

// Encode using the best available encoder
byte[] pngBytes;
if (useAVX2) {
    pngBytes = FPNGEEncoder.encode(image, 4, FPNGE_COMPRESS_LEVEL_DEFAULT);
} else {
    pngBytes = FPNGEncoder.encode(image, 4, 0);
}

Extracting Raw Pixel Bytes¶

Both encoders accept the raw byte[] from Java’s DataBufferByte directly. The C side handles the channel swap from Java’s native ABGR/BGR format to RGBA/RGB.

If your BufferedImage is already TYPE_4BYTE_ABGR or TYPE_3BYTE_BGR, you can extract the backing array with zero copy:

import java.awt.image.DataBufferByte;

byte[] raw = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();

For images in other formats (e.g. TYPE_INT_ARGB), convert first:

BufferedImage converted = new BufferedImage(
        image.getWidth(), image.getHeight(), BufferedImage.TYPE_4BYTE_ABGR);
Graphics g = converted.getGraphics();
g.drawImage(image, 0, 0, null);
g.dispose();
byte[] raw = ((DataBufferByte) converted.getRaster().getDataBuffer()).getData();

Publishing to Maven Central¶

Credentials go in ~/.gradle/gradle.properties:

sonatypeUsername=<your-central-portal-token-username>
sonatypePassword=<your-central-portal-token-password>

Then publish:

./gradlew publish