Added the option to generate the webp file without alpha. (#270)

scrimage-webp/src/main/java/com/sksamuel/scrimage/webp/CWebpHandler.java

@@ -28,7 +28,7 @@ public class CWebpHandler extends WebpHandler {
     * <p>
     * Binaries can be downloaded here:
     * https://storage.googleapis.com/downloads.webmproject.org/releases/webp/index.html
-    *
+    * <p>
     * This method is executed automatically but can also be invoked manually to check
     * for any installation errors.
     */
@@ -40,12 +40,13 @@ public byte[] convert(byte[] bytes,
                          int m,
                          int q,
                          int z,
-                         boolean lossless) throws IOException {
+                         boolean lossless,
+                         boolean withoutAlpha) throws IOException {
       Path input = Files.createTempFile("input", "webp").toAbsolutePath();
       Path output = Files.createTempFile("to_webp", "webp").toAbsolutePath();
       try {
          Files.write(input, bytes, StandardOpenOption.CREATE);
-         convert(input, output, m, q, z, lossless);
+         convert(input, output, m, q, z, lossless, withoutAlpha);
          return Files.readAllBytes(output);
       } finally {
          try {
@@ -64,7 +65,8 @@ private void convert(Path input,
                         int m,
                         int q,
                         int z,
-                        boolean lossless) throws IOException {
+                        boolean lossless,
+                        boolean withoutAlpha) throws IOException {
 
       Path stdout = Files.createTempFile("stdout", "webp");
       List<String> commands = new ArrayList<>();
@@ -84,6 +86,9 @@ private void convert(Path input,
       if (lossless) {
          commands.add("-lossless");
       }
+      if (withoutAlpha) {
+         commands.add("-noalpha");
+      }
       commands.add(input.toAbsolutePath().toString());
       commands.add("-o");
       commands.add(target.toAbsolutePath().toString());

scrimage-webp/src/main/java/com/sksamuel/scrimage/webp/WebpWriter.java

@@ -19,46 +19,61 @@ public class WebpWriter implements ImageWriter {
    private final int q;
    private final int m;
    private final boolean lossless;
+   private final boolean noAlpha;
 
    public WebpWriter() {
       z = -1;
       q = -1;
       m = -1;
       lossless = false;
+      noAlpha = false;
    }
 
    public WebpWriter(int z, int q, int m, boolean lossless) {
       this.z = z;
       this.q = q;
       this.m = m;
       this.lossless = lossless;
+      this.noAlpha = false;
+   }
+
+   public WebpWriter(int z, int q, int m, boolean lossless, boolean noAlpha) {
+      this.z = z;
+      this.q = q;
+      this.m = m;
+      this.lossless = lossless;
+      this.noAlpha = noAlpha;
    }
 
    public WebpWriter withLossless() {
       return new WebpWriter(z, q, m, true);
    }
 
+   public WebpWriter withoutAlpha() {
+      return new WebpWriter(z, q, m, lossless, true);
+   }
+
    public WebpWriter withQ(int q) {
       if (q < 0) throw new IllegalArgumentException("q must be between 0 and 100");
       if (q > 100) throw new IllegalArgumentException("q must be between 0 and 100");
-      return new WebpWriter(z, q, m, lossless);
+      return new WebpWriter(z, q, m, lossless, noAlpha);
    }
 
    public WebpWriter withM(int m) {
       if (m < 0) throw new IllegalArgumentException("m must be between 0 and 6");
       if (m > 6) throw new IllegalArgumentException("m must be between 0 and 6");
-      return new WebpWriter(z, q, m, lossless);
+      return new WebpWriter(z, q, m, lossless, noAlpha);
    }
 
    public WebpWriter withZ(int z) {
       if (z < 0) throw new IllegalArgumentException("z must be between 0 and 9");
       if (z > 9) throw new IllegalArgumentException("z must be between 0 and 9");
-      return new WebpWriter(z, q, m, lossless);
+      return new WebpWriter(z, q, m, lossless, noAlpha);
    }
 
    @Override
    public void write(AwtImage image, ImageMetadata metadata, OutputStream out) throws IOException {
-      byte[] bytes = handler.convert(image.bytes(PngWriter.NoCompression), m, q, z, lossless);
+      byte[] bytes = handler.convert(image.bytes(PngWriter.NoCompression), m, q, z, lossless, noAlpha);
       out.write(bytes);
    }
 }

scrimage-webp/src/test/kotlin/com/sksamuel/scrimage/webp/WebpTest.kt

@@ -23,6 +23,13 @@ class WebpTest : FunSpec() {
             javaClass.getResourceAsStream("/spacedock.webp").readBytes()
       }
 
+      test("no alpha") {
+         val webpWriter = WebpWriter.DEFAULT.withoutAlpha()
+         ImmutableImage.loader().fromResource("/alpha.png")
+            .bytes(webpWriter) shouldBe
+            javaClass.getResourceAsStream("/noAlpha.webp").readBytes()
+      }
+
       test("dwebp should capture error on failure") {
          val dwebpPath = WebpHandler.getBinaryPaths("dwebp")[2]