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ImageDescriptorBlock.as
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ImageDescriptorBlock.as
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/************************************************************************
* Copyright 2010-2011 Worlize Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
***********************************************************************/
package com.worlize.gif.blocks
{
import com.worlize.gif.constants.BlockType;
import com.worlize.gif.errors.OutOfDataError;
import flash.utils.ByteArray;
import flash.utils.Endian;
import flash.utils.IDataInput;
public class ImageDescriptorBlock implements IGIFBlockCodec
{
public var offsetLeft:uint;
public var offsetTop:uint;
public var width:uint;
public var height:uint;
public var haslct:Boolean;
public var interlaced:Boolean;
public var lctSorted:Boolean;
public var reserved:uint;
public var lctNumColors:uint;
public function decode(stream:IDataInput):void {
if (stream.bytesAvailable < 9) {
throw new OutOfDataError("Out of data while reading image descriptor block.");
}
offsetLeft = stream.readUnsignedShort();
offsetTop = stream.readUnsignedShort();
width = stream.readUnsignedShort();
height = stream.readUnsignedShort();
packed = stream.readUnsignedByte();
}
public function encode(ba:ByteArray=null):ByteArray {
if (ba === null) {
ba = new ByteArray();
ba.endian = Endian.LITTLE_ENDIAN;
}
ba.writeByte(BlockType.IMAGE_DESCRIPTOR);
ba.writeShort(offsetLeft);
ba.writeShort(offsetTop);
ba.writeShort(width);
ba.writeShort(height);
ba.writeByte(packed);
return ba;
}
public function set packed(byte:uint):void {
haslct = Boolean(byte & 0x80);
interlaced = Boolean(byte & 0x40);
lctSorted = Boolean(byte & 0x20);
reserved = (byte & 0x18) >> 3;
lctNumColors = 2 << (byte & 0x07);
}
public function get packed():uint {
var byte:uint = 0;
if (haslct) {
byte |= 0x80
}
if (interlaced) {
byte |= 0x40;
}
if (lctSorted) {
byte |= 0x20;
}
byte |= ((reserved & 0x03) << 3);
switch (lctNumColors) {
case 2:
byte |= 0;
break;
case 4:
byte |= 1;
break;
case 8:
byte |= 2;
break;
case 16:
byte |= 3;
break;
case 32:
byte |= 4;
break;
case 64:
byte |= 5;
break;
case 128:
byte |= 6;
break;
case 256:
byte |= 7;
break;
default:
throw new Error("Invalid local color table size: " + lctNumColors);
break;
}
return byte;
}
public function dispose():void {
}
}
}