diff --git a/src/main/java/com/baislsl/png/chunk/Chunk.java b/src/main/java/com/baislsl/png/chunk/Chunk.java
index eb4f975..1a50dd0 100644
--- a/src/main/java/com/baislsl/png/chunk/Chunk.java
+++ b/src/main/java/com/baislsl/png/chunk/Chunk.java
@@ -6,58 +6,57 @@ import com.baislsl.png.util.ByteHandler;
  * Created by baislsl on 17-7-9.
  */
 public class Chunk {
-    protected long length;
-    protected ChunkType type;
-    protected byte[] data;
-    protected byte[] crc = new byte[4];
+	protected long length;
+	protected ChunkType type;
+	protected byte[] data;
+	protected byte[] crc = new byte[4];
 
-    public byte[] dump() {
-        byte[] output = new byte[4 + 4 + data.length + 4];
-        Byte[] lengthBytes = new Byte[4];
-        for (int i = 0; i < 4; i++) {
-            output[3 - i] = (byte) (length & 0xff);
-        }
-        String typeName = type.name().toUpperCase();
-        for (int i = 0; i < 4; i++) {
-            output[4 + i] = (byte) typeName.charAt(i);
-        }
-        System.arraycopy(data, 0, output, 8, data.length);
-        System.arraycopy(crc, 0, output, output.length - crc.length, crc.length);
-        return output;
-    }
+	public byte[] dump() {
+		byte[] output = new byte[4 + 4 + data.length + 4];
+		Byte[] lengthBytes = new Byte[4];
+		for (int i = 0; i < 4; i++) {
+			output[3 - i] = (byte) (length & 0xff);
+		}
+		String typeName = type.name().toUpperCase();
+		for (int i = 0; i < 4; i++) {
+			output[4 + i] = (byte) typeName.charAt(i);
+		}
+		System.arraycopy(data, 0, output, 8, data.length);
+		System.arraycopy(crc, 0, output, output.length - crc.length, crc.length);
+		return output;
+	}
 
+	protected Chunk(byte[] length, byte[] type, byte[] data, byte[] crc) {
+		this.length = ByteHandler.byteToLong(length);
+		this.data = data;
+		this.crc = crc;
 
-    protected Chunk(byte[] length, byte[] type, byte[] data, byte[] crc) {
-        this.length = ByteHandler.byteToLong(length);
-        this.data = data;
-        this.crc = crc;
+		for (ChunkType chunkType : ChunkType.values()) {
+			if (chunkType.name().equals(ByteHandler.byteToString(type))) {
+				this.type = chunkType;
+				break;
+			}
+		}
 
-        for (ChunkType chunkType : ChunkType.values()) {
-            if (chunkType.name().equals(ByteHandler.byteToString(type))) {
-                this.type = chunkType;
-                break;
-            }
-        }
+	}
 
-    }
+	public long dataLength() {
+		return data.length;
+	}
 
-    public long dataLength() {
-        return data.length;
-    }
+	public long getLength() {
+		return length;
+	}
 
-    public long getLength() {
-        return length;
-    }
+	public ChunkType getType() {
+		return type;
+	}
 
-    public ChunkType getType() {
-        return type;
-    }
+	public byte[] getData() {
+		return data;
+	}
 
-    public byte[] getData() {
-        return data;
-    }
-
-    public byte[] getCrc() {
-        return crc;
-    }
+	public byte[] getCrc() {
+		return crc;
+	}
 }
diff --git a/src/main/java/com/baislsl/png/chunk/ChunkType.java b/src/main/java/com/baislsl/png/chunk/ChunkType.java
index 330f66a..91a3181 100644
--- a/src/main/java/com/baislsl/png/chunk/ChunkType.java
+++ b/src/main/java/com/baislsl/png/chunk/ChunkType.java
@@ -8,31 +8,37 @@ import com.baislsl.png.decode.PNG;
  */
 public enum ChunkType {
 
-    IHDR {
-        @Override
-        public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
-            png.setIhdr(new IHDR(length, type, data, crc));
-        }
-    },
-    PLTE {
-        @Override
-        public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
-            png.setPlte(new PLTE(length, type, data, crc));
-        }
-    },
-    IDAT {
-        @Override
-        public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
-            png.add(new IDAT(length, type, data, crc));
-        }
-    },
-    IEND {
-        @Override
-        public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
-            png.setIend(new IEND(length, type, data, crc));
-        }
-    };
+	IHDR {
+		@Override
+		public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+			png.setIhdr(new IHDR(length, type, data, crc));
+		}
+	},
+	tRNS {
+		@Override
+		public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+			png.setTrns(new tRNS(length, type, data, crc));
+		}
+	},
+	PLTE {
+		@Override
+		public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+			png.setPlte(new PLTE(length, type, data, crc));
+		}
+	},
+	IDAT {
+		@Override
+		public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+			png.add(new IDAT(length, type, data, crc));
+		}
+	},
+	IEND {
+		@Override
+		public void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+			png.setIend(new IEND(length, type, data, crc));
+		}
+	};
 
-    public abstract void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException;
+	public abstract void apply(PNG png, byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException;
 
 }
diff --git a/src/main/java/com/baislsl/png/chunk/IDAT.java b/src/main/java/com/baislsl/png/chunk/IDAT.java
index 91cd845..f8d93d5 100644
--- a/src/main/java/com/baislsl/png/chunk/IDAT.java
+++ b/src/main/java/com/baislsl/png/chunk/IDAT.java
@@ -5,7 +5,7 @@ package com.baislsl.png.chunk;
  */
 public class IDAT extends Chunk {
 
-    public IDAT(byte[] length, byte[] type, byte[] data, byte[] crc) {
-        super(length, type, data, crc);
-    }
+	public IDAT(byte[] length, byte[] type, byte[] data, byte[] crc) {
+		super(length, type, data, crc);
+	}
 }
diff --git a/src/main/java/com/baislsl/png/chunk/IEND.java b/src/main/java/com/baislsl/png/chunk/IEND.java
index 4f1861e..6132e60 100644
--- a/src/main/java/com/baislsl/png/chunk/IEND.java
+++ b/src/main/java/com/baislsl/png/chunk/IEND.java
@@ -4,7 +4,7 @@ package com.baislsl.png.chunk;
  * Created by baislsl on 17-7-9.
  */
 public class IEND extends Chunk {
-    public IEND(byte[] length, byte[] type, byte[] data, byte[] crc) {
-        super(length, type, data, crc);
-    }
+	public IEND(byte[] length, byte[] type, byte[] data, byte[] crc) {
+		super(length, type, data, crc);
+	}
 }
diff --git a/src/main/java/com/baislsl/png/chunk/IHDR.java b/src/main/java/com/baislsl/png/chunk/IHDR.java
index 6cb87d3..1c4e7d5 100644
--- a/src/main/java/com/baislsl/png/chunk/IHDR.java
+++ b/src/main/java/com/baislsl/png/chunk/IHDR.java
@@ -7,112 +7,113 @@ import com.baislsl.png.util.ByteHandler;
  * Created by baislsl on 17-7-9.
  */
 public class IHDR extends Chunk {
-    private long width, height;
-    private int bitDepth, colorType, compressionMethod, filterMethod, interlaceMethod;
+	private long width, height;
+	private int bitDepth, colorType, compressionMethod, filterMethod, interlaceMethod;
 
-    final private static int[] colorTypeValid = {0, 2, 3, 4, 6};
-    final private static int[][] mapColorBitDepth = {
-            {1, 2, 4, 8, 16},   // color type = 0
-            {},
-            {8, 16},            // color type = 2
-            {1, 2, 4, 8},       // color type = 3
-            {8, 16},            // color type = 4
-            {},
-            {8, 16}             // color type = 6
-    };
+	final private static int[] colorTypeValid = { 0, 2, 3, 4, 6 };
+	final private static int[][] mapColorBitDepth = { { 1, 2, 4, 8, 16 }, // color type = 0
+			{}, { 8, 16 }, // color type = 2
+			{ 1, 2, 4, 8 }, // color type = 3
+			{ 8, 16 }, // color type = 4
+			{}, { 8, 16 } // color type = 6
+	};
 
-    // the number of bytes per complete pixel, rounding up to one
-    public int getBpp() {
-        if (colorType == 2) {             // Each pixel is an R,G,B triple.
-            return 3;
-        } else if (colorType == 6) {      // Each pixel is an R,G,B triple, followed by an alpha sample.
-            return 4;
-        } else if (colorType == 3) {      // palette index, roll up to 1
-            return 1;
-        } else {
-            //LOG.error("Error when find bpp");
-            return 0;
-        }
-    }
+	// the number of bytes per complete pixel, rounding up to one
+	public int getBpp() {
+		if (colorType == 2) { // Each pixel is an R,G,B triple.
+			return 3;
+		} else if (colorType == 6) { // Each pixel is an R,G,B triple, followed by an alpha sample.
+			return 4;
+		} else if (colorType == 3) { // palette index, roll up to 1
+			return 1;
+		} else {
+			// LOG.error("Error when find bpp");
+			return 0;
+		}
+	}
 
-    public IHDR(byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
-        super(length, type, data, crc);
-        build();
-        checkLegal();
-    }
+	public IHDR(byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+		super(length, type, data, crc);
+		build();
+		checkLegal();
+	}
 
-    @Override
-    public String toString() {
-        StringBuilder sb = new StringBuilder();
-        sb.append("width=");sb.append(width);
-        sb.append("height=");sb.append(height);
-        sb.append("bitDepth=");sb.append(bitDepth);
-        sb.append("colorType=");sb.append(colorType);
-        sb.append("compressionMethod=");sb.append(compressionMethod);
-        sb.append("filterMethod=");sb.append(filterMethod);
-        sb.append("interlaceMethod=");sb.append(interlaceMethod);
-        return sb.toString();
-    }
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append("width=");
+		sb.append(width);
+		sb.append("height=");
+		sb.append(height);
+		sb.append("bitDepth=");
+		sb.append(bitDepth);
+		sb.append("colorType=");
+		sb.append(colorType);
+		sb.append("compressionMethod=");
+		sb.append(compressionMethod);
+		sb.append("filterMethod=");
+		sb.append(filterMethod);
+		sb.append("interlaceMethod=");
+		sb.append(interlaceMethod);
+		return sb.toString();
+	}
 
+	private void build() {
+		this.width = ByteHandler.byteToLong(data);
+		this.height = ByteHandler.byteToLong(data, 4);
+		this.bitDepth = ((int) data[8]) & 0xFF;
+		this.colorType = ((int) data[9]) & 0xFF;
+		this.compressionMethod = ((int) data[10]) & 0xFF;
+		this.filterMethod = ((int) data[11]) & 0xFF;
+		this.interlaceMethod = ((int) data[12]) & 0xFF;
+	}
 
-    private void build() {
-        this.width = ByteHandler.byteToLong(data);
-        this.height = ByteHandler.byteToLong(data, 4);
-        this.bitDepth = ((int)data[8]) & 0xFF;
-        this.colorType = ((int)data[9]) & 0xFF;
-        this.compressionMethod = ((int)data[10]) & 0xFF;
-        this.filterMethod = ((int)data[11]) & 0xFF;
-        this.interlaceMethod = ((int)data[12]) & 0xFF;
-    }
+	private void checkLegal() throws DecodeException {
+		boolean legal = false;
+		for (int c : colorTypeValid) {
+			if (c == colorType) {
+				legal = true;
+				break;
+			}
+		}
+		if (!legal) {
+			throw new DecodeException("Initialize IHDR : color type not legal to be " + colorType);
+		}
+		for (int b : mapColorBitDepth[colorType]) {
+			if (b == bitDepth) {
+				return;
+			}
+		}
+		throw new DecodeException(
+				"Initialzie IHDR : bit depth " + bitDepth + " not valid matching color type " + colorType);
+	}
 
+	public long getWidth() {
+		return this.width;
+	}
 
-    private void checkLegal() throws DecodeException {
-        boolean legal = false;
-        for (int c : colorTypeValid) {
-            if (c == colorType) {
-                legal = true;
-                break;
-            }
-        }
-        if (!legal) {
-            throw new DecodeException("Initialize IHDR : color type not legal to be " + colorType);
-        }
-        for (int b : mapColorBitDepth[colorType]) {
-            if (b == bitDepth) {
-                return;
-            }
-        }
-        throw new DecodeException("Initialzie IHDR : bit depth " + bitDepth + " not valid matching color type " + colorType);
-    }
+	public long getHeight() {
+		return this.height;
+	}
 
+	public int getBitDepth() {
+		return bitDepth;
+	}
 
-    public long getWidth() {
-        return this.width;
-    }
+	public int getColorType() {
+		return colorType;
+	}
 
-    public long getHeight() {
-        return this.height;
-    }
+	public int getCompressionMethod() {
+		return compressionMethod;
+	}
 
-    public int getBitDepth() {
-        return bitDepth;
-    }
-
-    public int getColorType() {
-        return colorType;
-    }
-
-    public int getCompressionMethod() {
-        return compressionMethod;
-    }
-
-    public int getFilterMethod() {
-        return filterMethod;
-    }
-
-    public int getInterlaceMethod() {
-        return interlaceMethod;
-    }
+	public int getFilterMethod() {
+		return filterMethod;
+	}
 
+	public int getInterlaceMethod() {
+		return interlaceMethod;
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/chunk/PLTE.java b/src/main/java/com/baislsl/png/chunk/PLTE.java
index d8271ea..cb6a489 100644
--- a/src/main/java/com/baislsl/png/chunk/PLTE.java
+++ b/src/main/java/com/baislsl/png/chunk/PLTE.java
@@ -2,37 +2,34 @@ package com.baislsl.png.chunk;
 
 import com.baislsl.png.decode.DecodeException;
 
-
 /**
  * Created by baislsl on 17-7-9.
  */
 public class PLTE extends Chunk {
-    private int[] color;
+	private int[] color;
 
-    public PLTE(byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException{
-        super(length, type, data, crc);
-        build();
-    }
+	public PLTE(byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+		super(length, type, data, crc);
+		build();
+	}
 
+	private void build() throws DecodeException {
+		if (this.length % 3 != 0)
+			throw new DecodeException("PLTE length can not be divide by 3");
+		int size = (int) length / 3;
+		color = new int[size];
+		for (int i = 0; i < size; i++) {
+			color[i] = (((int) data[i * 3]) & 0xFF) << 16 | (((int) data[i * 3 + 1]) & 0xFF) << 8
+					| (((int) data[i * 3 + 2]) & 0xFF) | 0xFF000000;
+		}
+	}
 
-    private void build() throws DecodeException{
-        if(this.length % 3 != 0 )
-            throw new DecodeException("PLTE length can not be divide by 3");
-
-        int size = (int)length / 3;
-        color = new int[size];
-        for(int i=0;i<size;i++){
-            color[i] = (((int)data[i*3]) & 0xFF) << 16 | (((int)data[i*3 + 1]) & 0xFF) << 8 | (((int)data[i*3 + 2]) & 0xFF);
-        }
-    }
-
-    public int getColor(int i){
-        return color[i];
-    }
-
-    public int getPaletteSize(){
-        return color.length;
-    }
+	public int getColor(int i) {
+		return color[i];
+	}
 
+	public int getPaletteSize() {
+		return color.length;
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/chunk/tRNS.java b/src/main/java/com/baislsl/png/chunk/tRNS.java
new file mode 100644
index 0000000..bfca19d
--- /dev/null
+++ b/src/main/java/com/baislsl/png/chunk/tRNS.java
@@ -0,0 +1,18 @@
+package com.baislsl.png.chunk;
+
+import com.baislsl.png.decode.DecodeException;
+
+/**
+ * Created by baislsl on 17-7-9.
+ */
+public class tRNS extends Chunk {
+
+	public tRNS(byte[] length, byte[] type, byte[] data, byte[] crc) throws DecodeException {
+		super(length, type, data, crc);
+	}
+
+	public int getAlpha() {
+		return (int)data[0] & 0xFF;
+	}
+
+}
diff --git a/src/main/java/com/baislsl/png/decode/DecodeException.java b/src/main/java/com/baislsl/png/decode/DecodeException.java
index 2dc088d..63f287b 100644
--- a/src/main/java/com/baislsl/png/decode/DecodeException.java
+++ b/src/main/java/com/baislsl/png/decode/DecodeException.java
@@ -5,17 +5,18 @@ package com.baislsl.png.decode;
  */
 public class DecodeException extends Exception {
 
-    public DecodeException() {}
+	public DecodeException() {
+	}
 
-    public DecodeException(String message) {
-        super(message);
-    }
+	public DecodeException(String message) {
+		super(message);
+	}
 
-    public DecodeException(String message, Throwable cause) {
-        super(message, cause);
-    }
+	public DecodeException(String message, Throwable cause) {
+		super(message, cause);
+	}
 
-    public DecodeException(Throwable cause) {
-        super(cause);
-    }
+	public DecodeException(Throwable cause) {
+		super(cause);
+	}
 }
diff --git a/src/main/java/com/baislsl/png/decode/Decoder.java b/src/main/java/com/baislsl/png/decode/Decoder.java
index 0349632..bcb3552 100644
--- a/src/main/java/com/baislsl/png/decode/Decoder.java
+++ b/src/main/java/com/baislsl/png/decode/Decoder.java
@@ -13,88 +13,84 @@ import static com.baislsl.png.util.ByteHandler.byteToLong;
  * Created by baislsl on 17-7-9.
  */
 public class Decoder {
-    //private final static Logger LOG = LoggerFactory.getLogger(Decoder.class);
-    private final InputStream in;
+	// private final static Logger LOG = LoggerFactory.getLogger(Decoder.class);
+	private final InputStream in;
 
-    private final static char[] head = {
-            0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a
-    };
+	private final static char[] head = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
 
-    public Decoder(InputStream in) {
-        this.in = in;
-    }
+	public Decoder(InputStream in) {
+		this.in = in;
+	}
 
-    private void readHeader() throws DecodeException, IOException {
-        byte[] header = readBytes(8);
-        for (int i = 0; i < 8; i++) {
-            if ((header[i] & 0xff) != (int) head[i])
-                throw new DecodeException("It seems that this is not a PNG files");
-        }
-        //LOG.info(ByteHandler.byteToString(header));
-    }
+	private void readHeader() throws DecodeException, IOException {
+		byte[] header = readBytes(8);
+		for (int i = 0; i < 8; i++) {
+			if ((header[i] & 0xff) != (int) head[i])
+				throw new DecodeException("It seems that this is not a PNG files");
+		}
+		// LOG.info(ByteHandler.byteToString(header));
+	}
 
-    private boolean readChunk(PNG png, String chunkName,
-                              byte[] length, byte[] type,
-                              byte[] data, byte[] crc) throws IOException, DecodeException {
-        for (ChunkType chunkType : ChunkType.values()) {
-            if (chunkType.name().equals(chunkName)) {
-                chunkType.apply(png, length, type, data, crc);
-                return true;
-            }
-        }
-        return false;
-    }
+	private boolean readChunk(PNG png, String chunkName, byte[] length, byte[] type, byte[] data, byte[] crc)
+			throws IOException, DecodeException {
+		for (ChunkType chunkType : ChunkType.values()) {
+			if (chunkType.name().equalsIgnoreCase(chunkName)) {
+				chunkType.apply(png, length, type, data, crc);
+				return true;
+			}
+		}
+		return false;
+	}
 
-    private boolean checkCrc(byte[] data, long crcNumber) {
-        return crcNumber == CRC.crc(data, data.length);
-    }
+	private boolean checkCrc(byte[] data, long crcNumber) {
+		return crcNumber == CRC.crc(data, data.length);
+	}
 
-    private boolean checkCrc(byte[] type, byte[] data, byte[] crc) {
-        long crcNumber = byteToLong(crc);
-        byte[] crcData = new byte[4 + data.length];
-        System.arraycopy(type, 0, crcData, 0, 4);
-        System.arraycopy(data, 0, crcData, 4, data.length);
+	private boolean checkCrc(byte[] type, byte[] data, byte[] crc) {
+		long crcNumber = byteToLong(crc);
+		byte[] crcData = new byte[4 + data.length];
+		System.arraycopy(type, 0, crcData, 0, 4);
+		System.arraycopy(data, 0, crcData, 4, data.length);
 
-        return checkCrc(crcData, crcNumber);
-    }
+		return checkCrc(crcData, crcNumber);
+	}
 
-    public PNG readInPNG() throws IOException, DecodeException {
-        PNG png = new PNG();
-        readHeader();
+	public PNG readInPNG() throws IOException, DecodeException {
+		PNG png = new PNG();
+		readHeader();
 
-        String chunkName;
-        do {
-            byte[] length = readBytes(4);
-            long size = byteToLong(length);
-            byte[] type = readBytes(4);
-            chunkName = ByteHandler.byteToString(type).toUpperCase();
-            if("IEND".equals(chunkName)) {
-            	break;
-            }
-            byte[] data = readBytes((int) size);
-            byte[] crc = readBytes(4);
-            //LOG.info(ByteHandler.byteToString(type));
+		String chunkName;
+		do {
+			byte[] length = readBytes(4);
+			long size = byteToLong(length);
+			byte[] type = readBytes(4);
+			chunkName = ByteHandler.byteToString(type).toUpperCase();
+			if ("IEND".equals(chunkName)) {
+				break;
+			}
+			byte[] data = readBytes((int) size);
+			byte[] crc = readBytes(4);
+			// LOG.info(ByteHandler.byteToString(type));
 
-            boolean found = readChunk(png, chunkName, length, type, data, crc);
-            if (!found) {
-                //LOG.info("Not support chunk name {}", chunkName);
-            }
+			boolean found = readChunk(png, chunkName, length, type, data, crc);
+			if (!found) {
+				// LOG.info("Not support chunk name {}", chunkName);
+			}
 
-            boolean crcMatch = checkCrc(type, data, crc);
-            if (!crcMatch) {
-                throw new DecodeException("Error data stream for incorrect crc");
-            }
-        } while (!"IEND".equals(chunkName));
-        return png;
-    }
-
-
-    private byte[] readBytes(int size) throws IOException {
-        byte[] result = new byte[size];
-        int ret = in.read(result, 0, size);
-        if (ret == -1) return null;
-        return result;
-    }
+			boolean crcMatch = checkCrc(type, data, crc);
+			if (!crcMatch) {
+				throw new DecodeException("Error data stream for incorrect crc");
+			}
+		} while (!"IEND".equals(chunkName));
+		return png;
+	}
 
+	private byte[] readBytes(int size) throws IOException {
+		byte[] result = new byte[size];
+		int ret = in.read(result, 0, size);
+		if (ret == -1)
+			return null;
+		return result;
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/decode/IDATManager.java b/src/main/java/com/baislsl/png/decode/IDATManager.java
index 545cc70..a62ac41 100644
--- a/src/main/java/com/baislsl/png/decode/IDATManager.java
+++ b/src/main/java/com/baislsl/png/decode/IDATManager.java
@@ -6,18 +6,18 @@ import java.util.ArrayList;
 
 public class IDATManager extends ArrayList<IDAT> {
 
-    public byte[] getIDATData() {
-        int dataSize = 0;
-        for (IDAT idat : this) {
-            dataSize += idat.dataLength();
-        }
-        byte[] data = new byte[dataSize];
-        int curPos = 0;
-        for (IDAT idat : this) {
-            System.arraycopy(idat.getData(), 0, data, curPos, (int) idat.dataLength());
-            curPos += idat.dataLength();
-        }
-        return data;
-    }
+	public byte[] getIDATData() {
+		int dataSize = 0;
+		for (IDAT idat : this) {
+			dataSize += idat.dataLength();
+		}
+		byte[] data = new byte[dataSize];
+		int curPos = 0;
+		for (IDAT idat : this) {
+			System.arraycopy(idat.getData(), 0, data, curPos, (int) idat.dataLength());
+			curPos += idat.dataLength();
+		}
+		return data;
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/decode/PNG.java b/src/main/java/com/baislsl/png/decode/PNG.java
index b8ecabc..aca2767 100644
--- a/src/main/java/com/baislsl/png/decode/PNG.java
+++ b/src/main/java/com/baislsl/png/decode/PNG.java
@@ -11,112 +11,122 @@ import java.io.IOException;
  * Created by baislsl on 17-7-9.
  */
 public class PNG {
-    //private final static Logger LOG = LoggerFactory.getLogger(PNG.class);
-    public IHDR ihdr;
-    public IDATManager idats = new IDATManager();
-    public PLTE plte;
-    public IEND iend;
+	// private final static Logger LOG = LoggerFactory.getLogger(PNG.class);
+	public IHDR ihdr;
+	public IDATManager idats = new IDATManager();
+	public PLTE plte;
+	public tRNS trns;
+	public IEND iend;
 
-    public PNG() {
-    }
+	public PNG() {
+	}
+	
+	public boolean isAlpha() {
+		return this.trns != null || ihdr.getBpp() == 4;
+	}
 
-    public PNG(IHDR ihdr, IDATManager idats, PLTE plte, IEND iend) {
-        this.ihdr = ihdr;
-        this.idats = idats;
-        this.plte = plte;
-        this.iend = iend;
-    }
+	public int[] getColor() throws DecodeException {
+		byte[] rawData = idats.getIDATData();
+		byte[] uncompressData = applyLZ77(rawData);
+		byte[][] transferData = applyReverseFilter(uncompressData);
+		int[] colors = applyColorTransfer(transferData);
+		return colors;
+	}
 
-    public int[] getColor() throws DecodeException {
-        byte[] rawData = idats.getIDATData();
-        byte[] uncompressData = applyLZ77(rawData);
-        byte[][] transferData = applyReverseFilter(uncompressData);
-        int[] colors = applyColorTransfer(transferData);
-        return colors;
-    }
+	private int[] applyColorTransfer(byte[][] data) throws DecodeException {
+		int bpp = ihdr.getBpp();
+		int width = (int) ihdr.getWidth();
+		int height = (int) ihdr.getHeight();
+		int colorType = ihdr.getColorType();
+		int bitDepth = ihdr.getBitDepth();
+		int[] colors = new int[width * height];
+		for (int i = 0; i < height; i++) {
+			for (int j = 0; j < width; j++) {
+				int idx = i * width + j;
+				switch (colorType) {
+				case 2:
+					if (bitDepth == 8) { // bpp = 3
+						colors[idx] = ((int) data[i][bpp * j] & 0xff) << 16 | ((int) data[i][bpp * j + 1] & 0xff) << 8
+								| ((int) data[i][bpp * j + 2] & 0xff);
+					} else {
+						throw new DecodeException("not supported");
+					}
+					break;
+				case 6:
+					if (bitDepth == 8) { // bpp = 4
+						colors[idx] = ((int) data[i][bpp * j] & 0xff) << 16 | ((int) data[i][bpp * j + 1] & 0xff) << 8
+								| ((int) data[i][bpp * j + 2] & 0xff) | ((int) data[i][bpp * j + 3] & 0xff) << 24;
+					} else {
+						throw new DecodeException("not supported");
+					}
+					break;
+				case 3:
+					int gap = 8 / bitDepth;
+					int a = (1 << bitDepth) - 1;
+					int b = gap - (j % gap) - 1;
+					int pi = (data[i][j / gap] >> (b * bitDepth)) & a;
+					if (trns != null && trns.getAlpha() == pi) {
+						colors[idx] = 0;
+					}else {
+						colors[idx] = plte.getColor(pi);
+					}
+					break;
+				default:
+					throw new DecodeException("Do not support color type " + colorType);
+				}
+			}
+		}
 
-    private int[] applyColorTransfer(byte[][] data) throws DecodeException {
-        int bpp = ihdr.getBpp();
-        int width = (int) ihdr.getWidth();
-        int height = (int) ihdr.getHeight();
-        int colorType = ihdr.getColorType();
-        int bitDepth = ihdr.getBitDepth();
-        int[] colors = new int[width * height];
-        for (int i = 0; i < height; i++) {
-            for (int j = 0; j < width; j++) {
-            	int idx = i * width + j;
-                switch (colorType) {
-                    case 2:
-                        if (bitDepth == 8) {  // bpp = 3
-                            colors[idx] = ((int)data[i][bpp * j] & 0xff) << 16 | ((int)data[i][bpp * j + 1] & 0xff) << 8 | ((int)data[i][bpp * j + 2] & 0xff);
-                        }else {
-                            throw new DecodeException("not supported");
-                        }
-                        break;
-                    case 6:
-                        if (bitDepth == 8) {  // bpp = 4
-                            colors[idx] = ((int)data[i][bpp * j] & 0xff) << 16 | ((int)data[i][bpp * j + 1] & 0xff) << 8 | ((int)data[i][bpp * j + 2] & 0xff) | ((int)data[i][bpp * j + 3] & 0xff) << 24;
-                        }else {
-                            throw new DecodeException("not supported");
-                        }
-                        break;
-                    case 3:
-                    	int gap = 8 / bitDepth;
-                    	int a = (1 << bitDepth) - 1;
-                    	colors[idx] = plte.getColor(data[i][j / gap] & a);
-                        break;
-                    default:
-                        throw new DecodeException("Do not support color type " + colorType);
-                }
-            }
-        }
+		return colors;
+	}
 
-        return colors;
-    }
+	private byte[] applyLZ77(byte[] data) throws DecodeException {
+		byte[] result;
+		try {
+			result = EaglerInflater.uncompress(data);
+		} catch (IOException e) {
+			// LOG.error("LZ77 decode error", e);
+			throw new DecodeException(e);
+		}
+		// LOG.info("Size after decode={}", result.length);
+		return result;
+	}
 
-    private byte[] applyLZ77(byte[] data) throws DecodeException {
-        byte[] result;
-        try {
-            result = EaglerInflater.uncompress(data);
-        } catch (IOException e) {
-            //LOG.error("LZ77 decode error", e);
-            throw new DecodeException(e);
-        }
-        //LOG.info("Size after decode={}", result.length);
-        return result;
-    }
+	private byte[][] applyReverseFilter(byte[] data) {
+		int width = (int) ihdr.getWidth(), height = (int) ihdr.getHeight();
+		return ReverseFilter.apply(data, width, height, ihdr.getBpp());
+	}
 
-    private byte[][] applyReverseFilter(byte[] data) {
-        int width = (int) ihdr.getWidth(), height = (int) ihdr.getHeight();
-        return ReverseFilter.apply(data, width, height, ihdr.getBpp());
-    }
+	public void setIdats(IDATManager idats) {
+		this.idats = idats;
+	}
 
-    public void setIdats(IDATManager idats) {
-        this.idats = idats;
-    }
+	public void setIhdr(IHDR ihdr) {
+		this.ihdr = ihdr;
+	}
 
-    public void setIhdr(IHDR ihdr) {
-        this.ihdr = ihdr;
-    }
+	public void setPlte(PLTE plte) {
+		this.plte = plte;
+	}
 
-    public void setPlte(PLTE plte) {
-        this.plte = plte;
-    }
+	public void setTrns(tRNS trns) {
+		this.trns = trns;
+	}
 
-    public void setIend(IEND iend) {
-        this.iend = iend;
-    }
+	public void setIend(IEND iend) {
+		this.iend = iend;
+	}
 
-    public void add(IDAT idat) throws DecodeException {
-        idats.add(idat);
-    }
+	public void add(IDAT idat) throws DecodeException {
+		idats.add(idat);
+	}
 
-    public long getWidth() {
-        return ihdr.getWidth();
-    }
+	public long getWidth() {
+		return ihdr.getWidth();
+	}
 
-    public long getHeight() {
-        return ihdr.getHeight();
-    }
+	public long getHeight() {
+		return ihdr.getHeight();
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/util/ByteHandler.java b/src/main/java/com/baislsl/png/util/ByteHandler.java
index ecc0172..8e07d1d 100644
--- a/src/main/java/com/baislsl/png/util/ByteHandler.java
+++ b/src/main/java/com/baislsl/png/util/ByteHandler.java
@@ -5,29 +5,28 @@ package com.baislsl.png.util;
  */
 public class ByteHandler {
 
-    public static long byteToLong(byte[] data, int offset, int size){
-        long result = 0;
-        for(int i=0;i<size;i++){
-            result <<= 8;
-            result |= ((long)data[offset + i] & 0xff);
-        }
-        return result;
-    }
+	public static long byteToLong(byte[] data, int offset, int size) {
+		long result = 0;
+		for (int i = 0; i < size; i++) {
+			result <<= 8;
+			result |= ((long) data[offset + i] & 0xff);
+		}
+		return result;
+	}
 
-    public static long byteToLong(byte[] data, int offset){
-        return byteToLong(data, offset, 4);
-    }
+	public static long byteToLong(byte[] data, int offset) {
+		return byteToLong(data, offset, 4);
+	}
 
-    public static long byteToLong(byte[] data) {
-        return byteToLong(data, 0,  4);
-    }
+	public static long byteToLong(byte[] data) {
+		return byteToLong(data, 0, 4);
+	}
 
-
-    public  static String byteToString(byte[] data) {
-        StringBuilder str = new StringBuilder();
-        for (byte b : data) {
-            str.append((char) (0x0ff & b));
-        }
-        return str.toString();
-    }
+	public static String byteToString(byte[] data) {
+		StringBuilder str = new StringBuilder();
+		for (byte b : data) {
+			str.append((char) (0x0ff & b));
+		}
+		return str.toString();
+	}
 }
diff --git a/src/main/java/com/baislsl/png/util/CRC.java b/src/main/java/com/baislsl/png/util/CRC.java
index bfe379f..1d95c27 100644
--- a/src/main/java/com/baislsl/png/util/CRC.java
+++ b/src/main/java/com/baislsl/png/util/CRC.java
@@ -4,33 +4,32 @@ package com.baislsl.png.util;
  * Created by baislsl on 17-7-9.
  */
 public class CRC {
-    private final static long[] crcTable = new long[256];
+	private final static long[] crcTable = new long[256];
 
-    static {
-        for (int i = 0; i < 256; i++) {
-            long c = i;
-            for (int k = 0; k < 8; k++) {
-                if ((c & 1) != 0) {
-                    c = 0xedb88320L ^ (c >> 1);
-                } else {
-                    c >>= 1;
-                }
-            }
-            crcTable[i] = c;
-        }
-    }
+	static {
+		for (int i = 0; i < 256; i++) {
+			long c = i;
+			for (int k = 0; k < 8; k++) {
+				if ((c & 1) != 0) {
+					c = 0xedb88320L ^ (c >> 1);
+				} else {
+					c >>= 1;
+				}
+			}
+			crcTable[i] = c;
+		}
+	}
 
+	private static long updateCrc(long crc, byte[] buf, int size) {
+		long ans = crc;
+		for (int i = 0; i < size; i++) {
+			ans = crcTable[(int) ((ans ^ buf[i]) & 0xff)] ^ (ans >> 8);
+		}
+		return ans;
+	}
 
-    private static long updateCrc(long crc, byte[] buf, int size){
-        long ans = crc;
-        for(int i=0;i<size;i++){
-            ans = crcTable[(int)((ans^buf[i])&0xff)] ^ (ans >> 8);
-        }
-        return ans;
-    }
-
-    public static long crc(byte[] buf, int size){
-        return updateCrc(0xffffffffL, buf, size) ^ 0xffffffffL;
-    }
+	public static long crc(byte[] buf, int size) {
+		return updateCrc(0xffffffffL, buf, size) ^ 0xffffffffL;
+	}
 
 }
diff --git a/src/main/java/com/baislsl/png/util/ReverseFilter.java b/src/main/java/com/baislsl/png/util/ReverseFilter.java
index 74fa99d..9016fdc 100644
--- a/src/main/java/com/baislsl/png/util/ReverseFilter.java
+++ b/src/main/java/com/baislsl/png/util/ReverseFilter.java
@@ -1,63 +1,64 @@
 package com.baislsl.png.util;
 
-
-
 public class ReverseFilter {
-    private ReverseFilter(){}
-    
-    private static int paethPredictor(int a, int b, int c) {
-        int p = a + b - c;
-        int pa = Math.abs(p - a), pb = Math.abs(p - b), pc = Math.abs(p - c);
-        if (pa <= pb && pa <= pc) return a;
-        if (pb <= pc) return b;
-        return c;
-    }
+	private ReverseFilter() {
+	}
 
-    // apply reverse Filter Algorithms to byte data
-    // bpp = 3
-    public static byte[][] apply(byte[] data, int width, int height, int bpp) {
-        int[] filterType = new int[height];
-        int[][] blocks = new int[height][width * bpp];
-        int dataIndex = 0;
-        for (int i = 0; i < height; i++) {
-            filterType[i] = (int)(data[dataIndex++]) & 0xFF;
-            for (int j = 0; j < width * bpp; j++) {
-                blocks[i][j] = (int)(data[dataIndex++]) & 0xFF;
-            }
-        }
-        for (int i = 0; i < height; i++) {
-            for (int j = 0; j < width * bpp; j++) {
-                int prior = (i == 0) ? 0 : blocks[i - 1][j];
-                int rawBpp = (j < bpp) ? 0 : blocks[i][j - bpp];
-                int bppPrior = (i == 0 || j < bpp) ? 0 : blocks[i - 1][j - bpp];
-                switch (filterType[i]) {
-                    case 0: // none
-                        break;
-                    case 1: // sub
-                        blocks[i][j] = blocks[i][j] + rawBpp;
-                        break;
-                    case 2: // up
-                        blocks[i][j] = blocks[i][j] + prior;
-                        break;
-                    case 3: //average
-                        blocks[i][j] = blocks[i][j] + (rawBpp + prior) / 2;
-                        break;
-                    case 4: // paeth
-                        blocks[i][j] = blocks[i][j] + paethPredictor(rawBpp, prior, bppPrior);
-                        break;
-                    default:
-                }
-                blocks[i][j] &= 0xff;
-            }
-        }
+	private static int paethPredictor(int a, int b, int c) {
+		int p = a + b - c;
+		int pa = Math.abs(p - a), pb = Math.abs(p - b), pc = Math.abs(p - c);
+		if (pa <= pb && pa <= pc)
+			return a;
+		if (pb <= pc)
+			return b;
+		return c;
+	}
 
-        byte[][] result = new byte[height][width * bpp];
-        for (int i = 0; i < height; i++) {
-            for (int j = 0; j < width * bpp; j++) {
-                result[i][j] = (byte) blocks[i][j];
-            }
-        }
-        return result;
-    }
+	// apply reverse Filter Algorithms to byte data
+	// bpp = 3
+	public static byte[][] apply(byte[] data, int width, int height, int bpp) {
+		int[] filterType = new int[height];
+		int[][] blocks = new int[height][width * bpp];
+		int dataIndex = 0;
+		for (int i = 0; i < height; i++) {
+			filterType[i] = (int) (data[dataIndex++]) & 0xFF;
+			for (int j = 0; j < width * bpp; j++) {
+				blocks[i][j] = (int) (data[dataIndex++]) & 0xFF;
+			}
+		}
+		for (int i = 0; i < height; i++) {
+			for (int j = 0; j < width * bpp; j++) {
+				int prior = (i == 0) ? 0 : blocks[i - 1][j];
+				int rawBpp = (j < bpp) ? 0 : blocks[i][j - bpp];
+				int bppPrior = (i == 0 || j < bpp) ? 0 : blocks[i - 1][j - bpp];
+				switch (filterType[i]) {
+				case 0: // none
+					break;
+				case 1: // sub
+					blocks[i][j] = blocks[i][j] + rawBpp;
+					break;
+				case 2: // up
+					blocks[i][j] = blocks[i][j] + prior;
+					break;
+				case 3: // average
+					blocks[i][j] = blocks[i][j] + (rawBpp + prior) / 2;
+					break;
+				case 4: // paeth
+					blocks[i][j] = blocks[i][j] + paethPredictor(rawBpp, prior, bppPrior);
+					break;
+				default:
+				}
+				blocks[i][j] &= 0xff;
+			}
+		}
+
+		byte[][] result = new byte[height][width * bpp];
+		for (int i = 0; i < height; i++) {
+			for (int j = 0; j < width * bpp; j++) {
+				result[i][j] = (byte) blocks[i][j];
+			}
+		}
+		return result;
+	}
 
 }
diff --git a/src/main/java/net/lax1dude/eaglercraft/EaglerImage.java b/src/main/java/net/lax1dude/eaglercraft/EaglerImage.java
index 94a3331..049fdb5 100644
--- a/src/main/java/net/lax1dude/eaglercraft/EaglerImage.java
+++ b/src/main/java/net/lax1dude/eaglercraft/EaglerImage.java
@@ -39,7 +39,7 @@ public class EaglerImage {
 	public static final EaglerImage loadImage(byte[] file) {
 		try {
 			PNG p = (new Decoder(new ByteArrayInputStream(file))).readInPNG();
-			return new EaglerImage(p.getColor(), (int)p.getWidth(), (int)p.getHeight(), p.ihdr.getBpp() == 4);
+			return new EaglerImage(p.getColor(), (int)p.getWidth(), (int)p.getHeight(), p.isAlpha());
 		} catch (IOException e) {
 			e.printStackTrace();
 			return null;