PSD解析工具实现（七）

上面已经把图层的信息都已经拿到了，剩下的byteArray就是图片的通道数据，这里就根据它的通道长度信息来获取对应的值，从而组合成对应的像素生成图片。

Channel Image data一共包含两个部分：

Compression是图片的压缩格式，0是原始数据，未经过任何处理的，1是使用了RLE压缩格式。

这里只处理RLE压缩格式的情况：

for (i = 0; i < layerCount; i++) 
{
	layerVo = layerVect[i];
	layerVo.parsePixel(layerData);
}

public function parsePixel(ba:ByteArray):void
{
	var tempObj:Object;
	//RGBA通道数据数组，前面已经获取过每种通道的长度信息
	for (var i:int = 0; i < channelDataArr.length; i++) 
	{
		tempObj = channelDataArr[i];
		tempObj.compressedType = ba.readUnsignedShort();
		var pixelDataByte:ByteArray = new ByteArray();
//If the Layer’s Size, and therefore the data, is odd, a pad byte will be inserted at the end of the row.
		//放弃最后两个字节
		if (tempObj.channelLen - 2 > 1) 
		{
	ba.readBytes(pixelDataByte, 0, tempObj.channelLen - 2);
		}
	tempObj.pixelData = getRealPixelData(tempObj.compressedType, pixelDataByte);
	}
}

private function getRealPixelData(compress:int, data:ByteArray):ByteArray
{
	if(1 == compress)
	{ 
		//使用height是因为它是按照行来压缩的
		return decodeRLE(data, height); 
	}
	return data;
}
//解压缩		
public function decodeRLE(source : ByteArray, height : int) : ByteArray 
{
			source.position = 0;
			var lines : Array = new Array(height);
			var i : int = 0;
			var total : int;
			var size : int;
			for ( i = 0; i < height; ++i ) {
				size = source.readUnsignedShort();
				lines[i] = size;
				total += lines[i];
			}
			if (source.position + total != source.length) {
				throw new Error("rle decode error");
			}
			var target : ByteArray = new ByteArray();
			var length : int = 0;
			var j : int;
			var k : int;
			var n : int;
			var count : int;
			for ( i = 0; i < height; ++i ) {
				length = lines[i];
				j = 0;
				count = 0;
				while (j < length) {
					n = source.readByte();
					j++;
					if (n >= 0) {
						count = n + 1;
						for (k = 0;k < count;++k) {
							target.writeByte(source.readByte());
						}
						j += count;
					} else {
						count = 1 - n;
						var byte : int = source.readByte();
						for (k = 0;k < count;++k) {
							target.writeByte(byte);
						}
						j++;
					}
				}
			}
			return target;
		}

根据得到的每种颜色的值进行计算得到对应的像素值：

private static function createPic(layerVo:LayerVo):void
{
if(true == layerVo.isFolder || true == layerVo.isText) return;
var color:uint;
var alphaChannel:ByteArray = (layerVo.channelDataArr[0].pixelData as ByteArray);
var redChannel:ByteArray = (layerVo.channelDataArr[1].pixelData as ByteArray);
var greenChannel:ByteArray = (layerVo.channelDataArr[2].pixelData as ByteArray);
var blueChannel:ByteArray = (layerVo.channelDataArr[3].pixelData as ByteArray);
alphaChannel.position = redChannel.position = greenChannel.position = blueChannel.position = 0;
var bmd:BitmapData = new BitmapData(layerVo.width, layerVo.height);
bmd.lock();
//逐个像素计算颜色值
for (var h:int = 0; h < layerVo.height; h++) 
{
	for (var w:int = 0; w < layerVo.width; w++) 
	{
	var alpha:uint = alphaChannel.readUnsignedByte();
	var red:uint = redChannel.readUnsignedByte();
	var green:uint = greenChannel.readUnsignedByte();
	var blue:uint = blueChannel.readUnsignedByte();
	color = alpha << 24 |red << 16 |green << 8 | blue;
	bmd.setPixel32(w, h, color);
	}
}
bmd.unlock();
			
var url:String = File.desktopDirectory.nativePath + "/image/" + layerVo.layerName+".png";
//生成图片
FileUtil.createPng(url, bmd); 
}

这个东西讲的有点乱，直接发个整理过的xmind给需要的同学，自己跟着去研究吧：

http://pan.baidu.com/s/1ge8Dnnd