SimplePNG

A zero-dependency minimalist Java library for creating PNG files.

It is implemented in pure Java and independent of Java AWT (ImageIO). It can be easily used with Android or JavaFX.

Feature

• Support for Java 8+;
• No dependence, only needs the java.base module;
• Very small (< 20 KiB);
• Supports writing compressed or uncompressed PNG images;
• Support for optional alpha channels;
• Support writing PNG metadata.

Limitations

• Currently only true color images are supported, support for grayscale images is planned;
• Currently only 8bpc images are supported;
• PNG filter is not supported, it may be supported in the future;
• Color palette is not supported.

Adding SimplePNG to your build

Maven:

<dependency>
  <groupId>org.glavo</groupId>
  <artifactId>simple-png</artifactId>
  <version>0.3.0</version>
</dependency>

Gradle:

implementation("org.glavo:simple-png:0.3.0")

If you want to use it for JavaFX, you can include additional dependencies:

<dependency>
  <groupId>org.glavo</groupId>
  <artifactId>simple-png-javafx</artifactId>
  <version>0.3.0</version>
</dependency>

Gradle:

implementation("org.glavo:simple-png-javafx:0.3.0")

Usage

The core abstraction of SimplePNG represents the ArgbImage interface of true color images and the PNGWriter used to write images to the output stream.

This is a simple example:

int rgba(int r,int g,int b,int a) { return ((r << 16) | ((g) << 8) | ((b)) | ((a) << 24)); }

ArgbImage image = new ArgbImage() {
    public int getWidth() { return 250; }
    public int getHeight() { return 250; }
    public int getArgb(int x, int y) { return rgba(x & 255, y & 255, 128, (255 - ((x / 2) & 255))); }
}

try (PNGWriter writer = new PNGWriter(Files.newOutputStream(Paths.get("gradient.png")))) {
    writer.write(image);
}

Result:

In addition to directly implementing the ArgbImage interface, SimplePNG also has some ArgbImage built-in implementations to facilitate you to interact with Java AWT/JavaFX or draw pictures.

// Array-based writable image
ArgbImageBuffer buffer = new ArgbImageBuffer();
for (int x = 0; x < 250; x++) {
    for (int y = 0; y < 250; y++) {
        buffer.setArgb(x, y, (255 - ((x / 2) & 255)), x & 255, y & 255, 128);
    }
}

// Wrapper for javafx.scene.image.Image
ArgbImage fxImage = PNGJavaFXUtils.asArgbImage(new Image("image.jpg"));

PNGWriter

PNGWriter provides a set of configurable options.

By default, PNGWriter will write files using 32-bit color (8 bits per channel, with an alpha channel). You can remove the alpha channel by setting the type to RGB.

new PNGWriter(outputStream, PNGType.RGB)

By default, PNGWriter will compress images using the default compression level. You can modify the compression level of PNGWriter.

new PNGWriter(outputStream, 0)

The lowest compression level is 0, which means no compression; compression levels up to 9, take more time to compress but have the smallest end result.

Metadata

SimplePNG supports attaching metadata to PNG images.

ArgbImage image = ...;

PNGMetadata metadta = new PNGMetadata()
        .setAuthor("Glavo")
        .setComment("SimplePNG example image");

ArgbImage imageWithMetadata = image.withMetadata(metadata);

try (PNGWriter writer = ...) {
    writer.write(imageWithMetadata);
}

SimplePNG will write the metadata into PNG files.

Donate

If you like this library, donating to me is my greatest support!

Due to payment method restrictions, donations are currently only supported through payment channels in Chinese mainland (微信，支付宝，爱发电等).

Here are the ways to donate: 捐赠支持 Glavo

Especially thanks

Thanks to PLCT Lab for supporting me.

This project is developed using JetBrains IDEA. Thanks to JetBrains for providing me with a free license, which is a strong support for me.