add support for png images

src/main/java/eu/jonahbauer/raytracing/Main.java

@@ -1,7 +1,7 @@
 package eu.jonahbauer.raytracing;
 
 import eu.jonahbauer.raytracing.render.Camera;
-import eu.jonahbauer.raytracing.render.ImageIO;
+import eu.jonahbauer.raytracing.render.ImageFormat;
 import eu.jonahbauer.raytracing.scene.Scene;
 import eu.jonahbauer.raytracing.scene.Sphere;
 
@@ -17,6 +17,6 @@ public class Main {
         var camera = new Camera(512, 2, 16 / 9d);
 
         var image = camera.render(scene);
-        ImageIO.write(image, Path.of("scene-" + System.currentTimeMillis() + ".ppm"));
+        ImageFormat.PNG.write(image, Path.of("scene-" + System.currentTimeMillis() + ".png"));
     }
 }

src/main/java/eu/jonahbauer/raytracing/render/ImageFormat.java

@@ -0,0 +1,130 @@
+package eu.jonahbauer.raytracing.render;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.zip.CRC32;
+import java.util.zip.CheckedOutputStream;
+import java.util.zip.DeflaterOutputStream;
+
+public enum ImageFormat {
+    PPM {
+        @Override
+        public void write(@NotNull Image image, @NotNull OutputStream out) throws IOException {
+            try (var writer = new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.US_ASCII))) {
+                writer.write("P3\n");
+                writer.write(String.valueOf(image.width()));
+                writer.write(" ");
+                writer.write(String.valueOf(image.height()));
+                writer.write("\n255\n");
+
+                var it = image.pixels().iterator();
+                while (it.hasNext()) {
+                    var color = it.next();
+                    writer.write(String.valueOf(color.red()));
+                    writer.write(" ");
+                    writer.write(String.valueOf(color.green()));
+                    writer.write(" ");
+                    writer.write(String.valueOf(color.blue()));
+                    writer.write("\n");
+                }
+            }
+        }
+    },
+    PNG {
+        private static final byte[] MAGIC = new byte[] { (byte) 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
+        private static final int IHDR_LENGTH = 13;
+        private static final int IHDR_TYPE = 0x49484452;
+        private static final int IDAT_TYPE = 0x49444154;
+        private static final int IEND_TYPE = 0x49454E44;
+
+        @Override
+        public void write(@NotNull Image image, @NotNull OutputStream out) throws IOException {
+            try (var data = new NoCloseDataOutputStream(out); var _ = data.closeable()) {
+                data.write(MAGIC);
+
+                writeIHDR(image, data);
+                writeIDAT(image, data);
+                writeIEND(image, data);
+            }
+        }
+
+        private void writeIHDR(@NotNull Image image, @NotNull DataOutputStream data) throws IOException {
+            data.writeInt(IHDR_LENGTH);
+            try (
+                    var crc = new CheckedOutputStream(data, new CRC32());
+                    var ihdr = new DataOutputStream(crc)
+            ) {
+                ihdr.writeInt(IHDR_TYPE);
+                ihdr.writeInt(image.width()); // image width
+                ihdr.writeInt(image.height()); // image height
+                ihdr.writeByte(8); // bit depth
+                ihdr.writeByte(2); // color type
+                ihdr.writeByte(0); // compression method
+                ihdr.writeByte(0); // filter method
+                ihdr.writeByte(0); // interlace method
+                ihdr.flush();
+                data.writeInt((int) crc.getChecksum().getValue());
+            }
+        }
+
+        private void writeIDAT(@NotNull Image image, @NotNull DataOutputStream data) throws IOException {
+            try (
+                    var baos = new ByteArrayOutputStream();
+                    var crc = new CheckedOutputStream(baos, new CRC32());
+                    var idat = new DataOutputStream(crc)
+            ) {
+                idat.writeInt(IDAT_TYPE);
+
+                try (var deflate = new DataOutputStream(new DeflaterOutputStream(idat))) {
+                    var pixels = image.pixels().iterator();
+                    for (int i = 0; pixels.hasNext(); i = (i + 1) % image.width()) {
+                        if (i == 0) deflate.writeByte(0); // filter type
+                        var pixel = pixels.next();
+                        deflate.writeByte(pixel.red());
+                        deflate.writeByte(pixel.green());
+                        deflate.writeByte(pixel.blue());
+                    }
+                }
+
+                var bytes = baos.toByteArray();
+                data.writeInt(bytes.length);
+                data.write(bytes);
+                data.writeInt((int) crc.getChecksum().getValue());
+            }
+        }
+
+        private void writeIEND(@NotNull Image image, @NotNull DataOutputStream data) throws IOException {
+            data.writeInt(0);
+            data.writeInt(IEND_TYPE);
+            data.writeInt(0);
+        }
+
+        private static class NoCloseDataOutputStream extends DataOutputStream {
+            public NoCloseDataOutputStream(OutputStream out) {
+                super(out);
+            }
+
+            @Override
+            public void close() {
+                // do nothing
+            }
+
+            public Closeable closeable() {
+                return super::close;
+            }
+        }
+    },
+    ;
+
+    public void write(@NotNull Image image, @NotNull Path path) throws IOException {
+        try (var out = Files.newOutputStream(path)) {
+            write(image, out);
+        }
+    }
+
+    public abstract void write(@NotNull Image image, @NotNull OutputStream out) throws IOException;
+}

src/main/java/eu/jonahbauer/raytracing/render/ImageIO.java

@@ -1,34 +0,0 @@
-package eu.jonahbauer.raytracing.render;
-
-import org.jetbrains.annotations.NotNull;
-
-import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-
-public final class ImageIO {
-    private ImageIO() {
-        throw new UnsupportedOperationException();
-    }
-
-    public static void write(@NotNull Image image, @NotNull Path path) throws IOException {
-        try (var out = Files.newBufferedWriter(path)) {
-            out.write("P3\n");
-            out.write(String.valueOf(image.width()));
-            out.write(" ");
-            out.write(String.valueOf(image.height()));
-            out.write("\n255\n");
-
-            var it = image.pixels().iterator();
-            while (it.hasNext()) {
-                var color = it.next();
-                out.write(String.valueOf(color.red()));
-                out.write(" ");
-                out.write(String.valueOf(color.green()));
-                out.write(" ");
-                out.write(String.valueOf(color.blue()));
-                out.write("\n");
-            }
-        }
-    }
-}