improve gif decoder

apng/src/main/java/jp/juggler/apng/GifDecoder.kt

@@ -3,104 +3,70 @@ package jp.juggler.apng
 import java.io.InputStream
 import kotlin.math.min
 
-/**
- * Class GifDecoder - Decodes a GIF file into one or more frames.
- *
- * Example:
- *
- * <pre>
- * {@code
- *    GifDecoder d = new GifDecoder();
- *    d.read("sample.gif");
- *    int n = d.getFrameCount();
- *    for (int i = 0; i < n; i++) {
- *       BufferedImage frame = d.getFrame(i);  // frame i
- *       int t = d.getDelay(i);  // display duration of frame in milliseconds
- *       // do something with frame
- *    }
- * }
- * </pre>
- * No copyright asserted on the source code of this class.  May be used for
- * any purpose, however, refer to the Unisys LZW patent for any additional
- * restrictions.  Please forward any corrections to questions at fmsware.com.
- *
- * @author Kevin Weiner, FM Software; LZW decoder adapted from John Cristy's ImageMagick.
- * @version 1.03 November 2003
- *
- */
-
-class Rectangle(val x : Int, val y : Int, val w : Int, val h : Int)
-
-class GifFrame(val image : ApngBitmap, val delay : Int)
-
-private class Reader(val bis : InputStream) {
+class GifDecoder {
 	
-	var block = ByteArray(256) // current data block
-	var blockSize = 0 // block size
-	
-	// Reads a single byte from the input stream.
-	fun read() : Int = bis.read()
-	
-	fun readArray(ba:ByteArray,offset:Int=0,length:Int=ba.size-offset) =
-		bis.read(ba,offset,length)
-	
-	/**
-	 * Reads next 16-bit value, LSB first
-	 */
-	// read 16-bit value, LSB first
-	fun readShort() = read() or (read() shl 8)
-	
-	/**
-	 * Reads next variable length block from input.
-	 *
-	 * @return number of bytes stored in "buffer"
-	 */
-	fun readBlock() : ByteArray {
-		val blockSize = read()
-		this.blockSize = blockSize
-		var n = 0
-		while(n < blockSize) {
-			val delta = bis .read(block, n, blockSize - n)
-			if(delta == - 1) throw RuntimeException("unexpected EOS")
-			n += delta
+	private class Rectangle(var x : Int = 0, var y : Int = 0, var w : Int = 0, var h : Int = 0) {
+		fun set(x : Int, y : Int, w : Int, h : Int) {
+			this.x = x
+			this.y = y
+			this.w = w
+			this.h = h
 		}
-		return block
 	}
 	
-	/**
-	 * Skips variable length blocks up to and including
-	 * next zero length block.
-	 */
-	fun skip() {
-		do {
-			readBlock()
-		} while((blockSize > 0))
-	}
-	
-	// read n byte and compose it to ascii string
-	fun string(n : Int) =
-		StringBuilder()
-			.apply {
-				for(i in 0 until n) {
-					append(read().toChar())
-				}
+	private class Reader(val bis : InputStream) {
+		
+		var block = ByteArray(256) // current data block
+		var blockSize = 0 // block size
+		
+		// Reads a single byte from the input stream.
+		fun byte() : Int = bis.read()
+		
+		// Reads next 16-bit value, LSB first
+		fun UInt16() = byte() or (byte() shl 8)
+		
+		fun array(ba : ByteArray, offset : Int = 0, length : Int = ba.size - offset) {
+			var nRead = 0
+			while(nRead < length) {
+				val delta = bis.read(ba, offset + nRead, length - nRead)
+				if(delta == - 1) throw RuntimeException("unexpected End of Stream")
+				nRead += delta
 			}
-			.toString()
-	
-}
-
-@Suppress("MemberVisibilityCanBePrivate", "unused")
-class GifDecoder(val callback: GifDecoderCallback) {
+		}
+		
+		// Reads specified bytes and compose it to ascii string
+		fun string(n : Int) : String {
+			val ba = ByteArray(n)
+			array(ba)
+			return ba.map { it.toChar() }.joinToString(separator = "")
+		}
+		
+		// Reads next variable length block
+		fun block() : ByteArray {
+			blockSize = byte()
+			array(block, 0, blockSize)
+			return block
+		}
+		
+		// Skips variable length blocks up to and including next zero length block.
+		fun skipBlock() {
+			do {
+				block()
+			} while(blockSize > 0)
+		}
+	}
 	
 	companion object {
 		
 		// max decoder pixel stack size
-		const val MaxStackSize = 4096
+		private const val MaxStackSize = 4096
 		
-		const val NullCode = - 1
+		private const val NullCode = - 1
 		
 		private const val b0 = 0.toByte()
 		
+		private const val OPAQUE = 0xff shl 24
+		
 	}
 	
 	private var width = 0 // full image width
@@ -109,8 +75,6 @@ class GifDecoder(val callback: GifDecoderCallback) {
 	private var loopCount = 1 // iterations; 0 = repeat forever
 	
 	private var gct : IntArray? = null // global color table
-	private var lct : IntArray? = null // local color table
-	private var act : IntArray? = null // active color table
 	
 	private var bgIndex = 0 // background color index
 	private var bgColor = 0 // background color
@@ -127,8 +91,7 @@ class GifDecoder(val callback: GifDecoderCallback) {
 	private var iw = 0  // current image rectangle
 	private var ih = 0  // current image rectangle
 	
-	private var lastRect : Rectangle? = null // last image rect
-	private var image : ApngBitmap? = null // current frame
+	private val lastRect : Rectangle = Rectangle() // last image rect
 	
 	// last graphic control extension info
 	private var dispose = 0
@@ -144,37 +107,109 @@ class GifDecoder(val callback: GifDecoderCallback) {
 	private var pixelStack : ByteArray? = null
 	private var pixels : ByteArray? = null
 	
-	private var frames = ArrayList<GifFrame>()  // frames read from current file
-	private var frameCount = 0
+	private val frames = ArrayList<Pair<ApngFrameControl, ApngBitmap>>()
 	
-	/////////////////////////////////////////////////////////////
-	// get decode result.
-	
-	/**
-	 * Gets the image contents of frame n.
-	 *
-	 * @return BufferedImage representation of frame, or null if n is invalid.
-	 */
-	@Suppress("MemberVisibilityCanBePrivate", "unused")
-	fun getFrame(n : Int) : ApngBitmap? {
-		frames?.let {
-			if(n in 0 until it.size) return it[n].image
-		}
-		return null
-	}
-	
-	/////////////////////////////////////////////////////////////
-	// private functions.
+	private var lastImage : ApngBitmap? = null
 	
+	// render to ApngBitmap
+	// may use some previous frame.
+	private fun render(destImage : ApngBitmap,act:IntArray) {
+		// expose destination image's pixels as int array
+		val dest = destImage.colors
+		val dest_w = destImage.width
+		
+		// fill in starting image contents based on last image's dispose code
+		if(lastDispose > 0) {
 
+			if(lastDispose == 3) {
+				// use image before last
+				val idx = frames.size - 2
+				lastImage = if(idx > 0) {
+					frames[idx-1].second
+				} else {
+					null
+				}
+			} else {
+				// lastDisposeが3以外でもlastImageはnullではない場合がある
+			}
+			
+			lastImage?.let{ lastImage ->
+
+				// copy pixels
+				System.arraycopy(lastImage.colors, 0, dest, 0, dest.size)
+				
+				if(lastDispose == 2) {
+					val fillColor = if(transparency) {
+						0 // assume background is transparent
+					} else {
+						lastBgColor // use given background color
+					}
+					
+					// fill lastRect
+					for(y in lastRect.y until lastRect.y + lastRect.h) {
+						val fillStart = y * dest_w + lastRect.x
+						val fillWidth = lastRect.w
+						dest.fill(fillColor, fromIndex = fillStart, toIndex = fillStart + fillWidth)
+					}
+				}
+
+			}
+		}
+		
+		// copy each source line to the appropriate place in the destination
+		var pass = 1
+		var inc = 8
+		var iline = 0
+		for(i in 0 until ih) {
+			var line = i
+			if(interlace) {
+				if(iline >= ih) {
+					when(++ pass) {
+						2 -> {
+							iline = 4
+						}
+						
+						3 -> {
+							iline = 2
+							inc = 4
+						}
+						
+						4 -> {
+							iline = 1
+							inc = 2
+						}
+					}
+				}
+				line = iline
+				iline += inc
+			}
+			line += iy
+			if(line < height) {
+				
+				// start of line in source
+				var sx = i * iw
+				
+				//
+				val k = line * width
+				
+				// loop for dest line.
+				for(dx in k + ix until min(k + width, k + ix + iw)) {
+					// map color and insert in destination
+					val index = pixels !![sx ++].toInt() and 0xff
+					val c = act[index]
+					if(c != 0) dest[dx] = c
+				}
+			}
+		}
+	}
 	
 	/**
 	 * Decodes LZW image data into pixel array.
 	 * Adapted from John Cristy's ImageMagick.
 	 */
-	private fun decodeImageData(reader:Reader) {
+	private fun decodeImageData(reader : Reader) {
 		
-		// Reallocate pizel array if need
+		// allocate pixel array if need
 		val npix = iw * ih
 		if((pixels?.size ?: 0) < npix) pixels = ByteArray(npix)
 		val pixels = this.pixels !!
@@ -187,9 +222,15 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		val pixelStack = this.pixelStack !!
 		
 		//  Initialize GIF data stream decoder.
-		val data_size = reader.read()
+		val data_size = reader.byte()
 		val clear = 1 shl data_size
 		val end_of_information = clear + 1
+		
+		var available = clear + 2
+		var old_code = NullCode
+		var code_size = data_size + 1
+		var code_mask = (1 shl code_size) - 1
+
 		for(code in 0 until clear) {
 			prefix[code] = 0
 			suffix[code] = code.toByte()
@@ -203,10 +244,6 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		var top = 0
 		var bi = 0
 		var pi = 0
-		var available = clear + 2
-		var old_code = NullCode
-		var code_size = data_size + 1
-		var code_mask = (1 shl code_size) - 1
 		
 		var i = 0
 		while(i < npix) {
@@ -215,9 +252,9 @@ class GifDecoder(val callback: GifDecoderCallback) {
 					//  Load bytes until there are enough bits for a code.
 					if(count == 0) {
 						// Read a new data block.
-						reader.readBlock()
+						reader.block()
 						count = reader.blockSize
-						if( count <= 0) break
+						if(count <= 0) break
 						bi = 0
 					}
 					datum += (reader.block[bi].toInt() and 0xff) shl bits
@@ -292,123 +329,27 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		}
 	}
 	
-	/**
-	 * Creates new frame image from current data (and previous
-	 * frames as specified by their disposition codes).
-	 */
-	private fun setPixels(destImage : ApngBitmap) {
-		// expose destination image's pixels as int array
-		val dest = destImage.colors
-		val dest_w = destImage.width
-		
-		// fill in starting image contents based on last image's dispose code
-		var lastImage : ApngBitmap? = null // previous frame
-		if(lastDispose > 0) {
-			if(lastDispose == 3) {
-				// use image before last
-				val n = frameCount - 2
-				if(n > 0) {
-					lastImage = getFrame(n - 1)
-				} else {
-					lastImage = null
-				}
-			}
-			
-		}
-		if(lastImage != null) {
-			// copy pixels
-			System.arraycopy(lastImage.colors, 0, dest, 0, dest.size)
-			
-			val lastRect = this.lastRect
-			if(lastDispose == 2 && lastRect != null) {
-				// fill lastRect
-				
-				val fillColor = if(transparency) {
-					0 // assume background is transparent
-				} else {
-					lastBgColor // use given background color
-				}
-				
-				for(y in lastRect.y until lastRect.y + lastRect.h) {
-					val fillStart = y * dest_w + lastRect.x
-					val fillWidth = lastRect.w
-					dest.fill(fillColor, fromIndex = fillStart, toIndex = fillStart + fillWidth)
-				}
-			}
-		}
-		
-		// copy each source line to the appropriate place in the destination
-		var pass = 1
-		var inc = 8
-		var iline = 0
-		for(i in 0 until ih) {
-			var line = i
-			if(interlace) {
-				if(iline >= ih) {
-					pass ++
-					when(++ pass) {
-						2 -> {
-							iline = 4
-							inc = 8
-						}
-						
-						3 -> {
-							iline = 2
-							inc = 4
-						}
-						
-						4 -> {
-							iline = 1
-							inc = 2
-						}
-					}
-				}
-				line = iline
-				iline += inc
-			}
-			line += iy
-			if(line < height) {
-				
-				// start of line in source
-				var sx = i * iw
-				
-				//
-				val k = line * width
-				
-				// loop for dest line.
-				for(dx in k + ix until min(k + width, k + ix + iw)) {
-					// map color and insert in destination
-					val index = pixels !![sx ++].toInt() and 0xff
-					val c = act !![index]
-					if(c != 0) dest[dx] = c
-				}
-			}
-		}
-	}
-	
 	/**
 	 * Reads color table as 256 RGB integer values
 	 *
 	 * @param nColors int number of colors to read
 	 * @return int array containing 256 colors (packed ARGB with full alpha)
 	 */
-	private fun readColorTable(reader:Reader,nColors : Int) : IntArray {
+	private fun parseColorTable(reader : Reader, nColors : Int) : IntArray {
 		val nBytes = 3 * nColors
 		val c = ByteArray(nBytes)
-		val n = reader.readArray(c)
-		if(n < nBytes) throw RuntimeException("unexpected EOS")
+		reader.array(c)
 		
 		// max size to avoid bounds checks
 		val tab = IntArray(256)
 		var i = 0
 		var j = 0
-		val opaque = 0xff shl 24
 		while(i < nColors) {
 			val r = c[j].toInt() and 255
 			val g = c[j + 1].toInt() and 255
 			val b = c[j + 2].toInt() and 255
 			j += 3
-			tab[i ++] = ( opaque or (r shl 16) or (g shl 8) or b)
+			tab[i ++] = (OPAQUE or (r shl 16) or (g shl 8) or b)
 		}
 		return tab
 	}
@@ -416,48 +357,43 @@ class GifDecoder(val callback: GifDecoderCallback) {
 	/**
 	 * Reads Graphics Control Extension values
 	 */
-	private fun readGraphicControlExt(reader:Reader) {
-		reader.read() // block size
-		
-		val packed = reader.read() // packed fields
-		
+	private fun parseGraphicControlExt(reader : Reader) {
+		reader.byte() // block size
+		val packed = reader.byte() // packed fields
 		dispose = (packed and 0x1c) shr 2 // disposal method
-		
 		// elect to keep old image if discretionary
 		if(dispose == 0) dispose = 1
 		
 		transparency = (packed and 1) != 0
-		
 		// delay in milliseconds
-		delay = reader.readShort() * 10
+		delay = reader.UInt16() * 10
 		// transparent color index
-		transIndex = reader.read()
-		
+		transIndex = reader.byte()
 		// block terminator
-		reader.read()
+		reader.byte()
 	}
 	
 	// Reads Netscape extension to obtain iteration count
-	private fun readNetscapeExt(reader:Reader) {
+	private fun readNetscapeExt(reader : Reader) {
 		do {
-			val block = reader.readBlock()
+			val block = reader.block()
 			if(block[0].toInt() == 1) {
 				// loop count sub-block
 				val b1 = block[1].toInt() and 255
 				val b2 = block[2].toInt() and 255
 				loopCount = ((b2 shl 8) and b1)
 			}
-		} while( reader.blockSize > 0 )
+		} while(reader.blockSize > 0)
 	}
 	
 	// Reads next frame image
-	private fun readImage(reader:Reader) {
-		ix = reader.readShort() // (sub)image position & size
-		iy = reader.readShort()
-		iw = reader.readShort()
-		ih = reader.readShort()
+	private fun parseFrame(reader : Reader) {
+		ix = reader.UInt16() // (sub)image position & size
+		iy = reader.UInt16()
+		iw = reader.UInt16()
+		ih = reader.UInt16()
 		
-		val packed = reader.read()
+		val packed = reader.byte()
 		lctFlag = (packed and 0x80) != 0 // 1 - local color table flag
 		interlace = (packed and 0x40) != 0 // 2 - interlace flag
 		// 3 - sort flag
@@ -465,63 +401,72 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		lctSize = 2 shl (packed and 7) // 6-8 - local color table size
 		
 		val act = if(lctFlag) {
-			lct = readColorTable(reader,lctSize) // read table
-			lct !! // make local table active
+			// make local table active
+			parseColorTable(reader, lctSize)
 		} else {
 			if(bgIndex == transIndex) bgColor = 0
 			gct !! // make global table active
 		}
 		
-		this.act = act
 		var save = 0
 		if(transparency) {
 			save = act[transIndex]
 			act[transIndex] = 0 // set transparent color if specified
 		}
 		
-		
 		decodeImageData(reader) // decode pixel data
-		reader.skip()
+		reader.skipBlock()
 		
-		++ frameCount
-		
-		// create new image to receive frame data
-		val image = ApngBitmap(width, height).apply {
-			setPixels(this) // transfer pixel data to image
+		val image = ApngBitmap(width, height).also {
+			render(it,act) // transfer pixel data to image
 		}
-		this.image = image
 		
-		frames.add(GifFrame(image, delay)) // add image to frame list
+		// add image to frame list
+		frames.add(
+			Pair(
+				ApngFrameControl(
+					width = width,
+					height = height,
+					xOffset = 0,
+					yOffset = 0,
+					disposeOp = DisposeOp.None,
+					blendOp = BlendOp.Source,
+					sequenceNumber = frames.size,
+					delayMilliseconds = delay.toLong()
+				),
+				image
+			)
+		)
 		
 		if(transparency) {
 			act[transIndex] = save
 		}
-
+		
 		/**
 		 * Resets frame state for reading next image.
 		 */
 		lastDispose = dispose
-		lastRect = Rectangle(ix, iy, iw, ih)
+		lastRect.set(ix, iy, iw, ih)
 		lastBgColor = bgColor
 		dispose = 0
 		transparency = false
 		delay = 0
-		lct = null
+		lastImage = image
 	}
 	
-	private fun readContents(reader : Reader) {
-		// read GIF file content blocks
+	// read GIF content blocks
+	private fun readContents(reader : Reader) : ApngAnimationControl {
 		loopBlocks@ while(true) {
-			when(val blockCode = reader.read()) {
+			when(val blockCode = reader.byte()) {
 				// image separator
-				0x2C -> readImage(reader)
+				0x2C -> parseFrame(reader)
 				// extension
-				0x21 -> when(reader.read()) {
+				0x21 -> when(reader.byte()) {
 					// graphics control extension
-					0xf9 -> readGraphicControlExt(reader)
+					0xf9 -> parseGraphicControlExt(reader)
 					// application extension
 					0xff -> {
-						val block = reader.readBlock()
+						val block = reader.block()
 						var app = ""
 						for(i in 0 until 11) {
 							app += block[i].toChar()
@@ -529,13 +474,13 @@ class GifDecoder(val callback: GifDecoderCallback) {
 						if(app == "NETSCAPE2.0") {
 							readNetscapeExt(reader)
 						} else {
-							reader.skip() // don't care
+							reader.skipBlock() // don't care
 						}
 					}
 					
 					else -> {
 						// uninteresting extension
-						reader.skip()
+						reader.skipBlock()
 					}
 				}
 				
@@ -549,23 +494,25 @@ class GifDecoder(val callback: GifDecoderCallback) {
 				else -> error("unknown block code $blockCode")
 			}
 		}
+		
+		return ApngAnimationControl(numFrames = frames.size, numPlays = loopCount)
 	}
 	
-	var header : ApngImageHeader? = null
-	var animationControl : ApngAnimationControl? = null
+	/**
+	 * Initializes or re-initializes reader
+	 */
+	private fun reset(){
+		frames.clear()
+		lastImage = null
+		loopCount = ApngAnimationControl.PLAY_INDEFINITELY
+	}
 	
 	/**
 	 * Reads GIF file header information.
 	 */
-	private fun readHeader(reader : Reader) {
+	private fun parseImageHeader(reader : Reader) : ApngImageHeader {
 		
-		/**
-		 * Initializes or re-initializes reader
-		 */
-		frameCount = 0
-		frames.clear()
-		lct = null
-		loopCount = ApngAnimationControl.PLAY_INDEFINITELY
+		reset()
 		
 		val id = reader.string(6)
 		if(! id.startsWith("GIF"))
@@ -574,14 +521,14 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		/**
 		 * Reads Logical Screen Descriptor
 		 */
-
+		
 		// logical screen size
-		width = reader.readShort()
-		height = reader.readShort()
-		if( width < 1 || height < 1) error("too small size. ${width}*${height}")
+		width = reader.UInt16()
+		height = reader.UInt16()
+		if(width < 1 || height < 1) error("too small size. ${width}*${height}")
 		
 		// packed fields
-		val packed = reader.read()
+		val packed = reader.byte()
 		
 		// global color table used
 		val gctFlag = (packed and 0x80) != 0 // 1   : global color table flag
@@ -589,19 +536,19 @@ class GifDecoder(val callback: GifDecoderCallback) {
 		// 5   : gct sort flag
 		gctSize = 2 shl (packed and 7) // 6-8 : gct size
 		
-		bgIndex = reader.read() // background color index
-		pixelAspect = reader.read() // pixel aspect ratio
+		bgIndex = reader.byte() // background color index
+		pixelAspect = reader.byte() // pixel aspect ratio
 		
 		gct = if(gctFlag) {
-			val table = readColorTable(reader,gctSize)
+			val table = parseColorTable(reader, gctSize)
 			bgColor = table[bgIndex]
 			table
-		}else{
+		} else {
 			bgColor = 0
 			null
 		}
 		
-		val header = ApngImageHeader(
+		return ApngImageHeader(
 			width = this.width,
 			height = this.height,
 			bitDepth = 8,
@@ -610,43 +557,22 @@ class GifDecoder(val callback: GifDecoderCallback) {
 			filterMethod = FilterMethod.Standard,
 			interlaceMethod = InterlaceMethod.None
 		)
-		this.header = header
+	}
+	
+	fun parse(src : InputStream, callback : GifDecoderCallback) {
+		val reader = Reader(src)
+		val header = parseImageHeader(reader)
+		val animationControl = readContents(reader)
+		
+		// GIFは最後まで読まないとフレーム数が分からない
+		if(frames.isEmpty()) throw error("there is no frame.")
 		
 		callback.onGifHeader(header)
-	}
-	
-	
-	@Suppress("MemberVisibilityCanBePrivate", "unused")
-	fun read(src : InputStream) {
-		val reader = Reader(src)
-		readHeader(reader)
-		readContents(reader)
-		
-		val header = this.header!!
-		if(frameCount < 0) throw error("frameCount < 0")
-		
-		// GIFは最後まで読まないとフレーム数が分からない？
-		// 最後まで読んでからフレーム数をコールバック
-		val animationControl = ApngAnimationControl(numFrames = frameCount,numPlays = loopCount)
-		this.animationControl = animationControl
-		callback.onGifAnimationInfo( header, animationControl)
-
-		// 各フレームを送る
-		var i=0
-		for(frame in frames){
-			val frameControl = ApngFrameControl(
-				width = header.width,
-				height = header.height,
-				xOffset = 0,
-				yOffset = 0,
-				disposeOp = DisposeOp.None,
-				blendOp = BlendOp.Source,
-				sequenceNumber=i++,
-				delayMilliseconds = frame.delay.toLong()
-			)
-			callback.onGifAnimationFrame(frameControl,frame.image)
+		callback.onGifAnimationInfo(header, animationControl)
+		for(frame in frames) {
+			callback.onGifAnimationFrame(frame.first, frame.second)
 		}
-		frames.clear()
+		
+		reset()
 	}
-	
-}
+}

apng_android/src/main/java/jp/juggler/apng/ApngFrames.kt

@@ -108,6 +108,7 @@ class ApngFrames private constructor(
 			}
 			
 		}
+		
 		private fun parseGif(
 			inStream : InputStream,
 			pixelSizeMax : Int,
@@ -115,7 +116,7 @@ class ApngFrames private constructor(
 		) : ApngFrames {
 			val result = ApngFrames(pixelSizeMax, debug)
 			try {
-				GifDecoder(result).read(inStream)
+				GifDecoder().parse(inStream, result)
 				result.onParseComplete()
 				return result.takeIf { result.defaultImage != null || result.frames?.isNotEmpty() == true }
 					?: throw RuntimeException("GIF has no image")
@@ -125,31 +126,31 @@ class ApngFrames private constructor(
 			}
 		}
 		
-		
-		// PNGヘッダを確認
-		
-		
 		@Suppress("unused")
 		fun parse(
 			pixelSizeMax : Int,
 			debug : Boolean = false,
-			opener: ()->InputStream?
+			opener : () -> InputStream?
 		) : ApngFrames? {
-			val buf = ByteArray(8){ 0.toByte() }
-			opener()?.use{ it.read(buf,0,buf.size) }
+			
+			val buf = ByteArray(8) { 0.toByte() }
+			opener()?.use { it.read(buf, 0, buf.size) }
+			
 			if(buf.size >= 8
 				&& (buf[0].toInt() and 0xff) == 0x89
 				&& (buf[1].toInt() and 0xff) == 0x50
 			) {
-				return opener()?.use{ parseApng(it,pixelSizeMax,debug) }
+				return opener()?.use { parseApng(it, pixelSizeMax, debug) }
 			}
+			
 			if(buf.size >= 6
 				&& buf[0].toChar() == 'G'
 				&& buf[1].toChar() == 'I'
 				&& buf[2].toChar() == 'F'
 			) {
-				return opener()?.use{ parseGif(it,pixelSizeMax,debug) }
+				return opener()?.use { parseGif(it, pixelSizeMax, debug) }
 			}
+			
 			return null
 		}
 	}
@@ -460,7 +461,6 @@ class ApngFrames private constructor(
 	}
 	
 	override fun onGifAnimationInfo(
-		
 		header : ApngImageHeader,
 		animationControl : ApngAnimationControl
 	) {
@@ -469,14 +469,12 @@ class ApngFrames private constructor(
 		}
 		this.animationControl = animationControl
 		this.frames = ArrayList(animationControl.numFrames)
-		
 		val canvasBitmap = createBlankBitmap(header.width, header.height)
 		this.canvasBitmap = canvasBitmap
 		this.canvas = Canvas(canvasBitmap)
 	}
 	
 	override fun onGifAnimationFrame(
-		
 		frameControl : ApngFrameControl,
 		frameBitmap : ApngBitmap
 	) {
@@ -488,9 +486,14 @@ class ApngFrames private constructor(
 		}
 		val frames = this.frames ?: return
 		
+		if(frames.isEmpty()) {
+			defaultImage?.recycle()
+			defaultImage = toAndroidBitmap(frameBitmap, pixelSizeMax)
+			// ここでwidth,heightがセットされる
+		}
+		
 		val frameBitmapAndroid = toAndroidBitmap(frameBitmap)
 		try {
-			
 			val frame = Frame(
 				bitmap = scaleBitmap(pixelSizeMax, frameBitmapAndroid, recycleSrc = false),
 				timeStart = timeTotal,