J2me中实现淡入淡出效果

J2me 中实现淡入淡出效果

飘飘白云 (l_zhaohui@163.com)

在 J2me 中实现淡入淡出效果，据我所知至少有三种方法。

第一种是取得需要变换图片的像素，依次 设 置 每 个象素的 alpha 通道 值 , 让它在 0~100 之间变化。

第二种是修改图片的调色板数据，让其在调色板原始数据到 255 之间变化。

第三种，其实也是利用上面的办法，先描画图片，然后在图片上覆盖一个黑色矩形，改变这个黑色矩形透明度就可以实现淡入淡出的效果。

前两种方法相比较的话，第一种方法运算量是比较大的，而且第一种方法由于 midp1.0 不支持 alpha 通道，在一些手机上无法实现。

下面给出第二种方法的示例，在我们开始之前，应该熟悉 png 文件格式，如果还不是很明白的话，可以 google 一下，或者查看前面的帖子中的相关连接。

代码很清楚，下面是源代码：

------------CODE__START-----------------------

import java.io.DataInputStream;

import java.util.Timer;

import java.util.TimerTask;

import javax.microedition.lcdui.Canvas;

import javax.microedition.lcdui.Display;

import javax.microedition.lcdui.Graphics;

import javax.microedition.lcdui.Image;

import javax.microedition.midlet.MIDlet;

import javax.microedition.midlet.MIDletStateChangeException;

/**

* Discription : 修改调色板数据实现淡入淡出效果

* Author : 飘飘白云 (l_zhaohui@163.com)

* Created date : 2006/07/13 18:06:39

* Modified history :

*/

public class PngFadeInOut extends MIDlet

{

GameCanvas canvas;

Display display;

public PngFadeInOut()

{

super();

try {

display = Display.getDisplay(this);

canvas = new GameCanvas(this);

} catch (Exception e) {}

}

protected void startApp() throws MIDletStateChangeException

{

if( canvas != null ){

display.setCurrent(canvas);

canvas.start();

}

}

protected void pauseApp()

{

canvas.isExit = true;

}

protected void destroyApp( boolean arg0) throws MIDletStateChangeException

{

}

}

class GameCanvas extends Canvas

{

static String imageName = "/fadeInOut.png";

public static final int MAX_TARDINESS = 30;

//---------------------------------------------------

PngFadeInOut app;

boolean isInited = false;

public boolean isExit = false;

Image offImage = null;

public Graphics g = null;

int scrW;

int scrH;

//---------------------------------------------------

int gameMode;

int subMode;

static final int smInit = 0;

static final int smProc = 1;

static final int smEnd = 2;

static final int gmStart = 0;

//---------------------------------------------------

Image testImage = null;

byte[] oldRGBData = null;

byte[] imgData = null;

static final int FADE_IN = 0;

static final int FADE_OUT = 1;

static final int FADE_STEP = 1;

static int fadeType = FADE_IN;

//---------------------------------------------------

//---Timer process

//---------------------------------------------------

TimerTask task;

Timer timer;

int timerDelayTime;

public boolean isTimerRunning;

void startTimer(int delayTime){

timerDelayTime = delayTime;

isTimerRunning = true;

timer = new Timer();

task = new ProcessingRunner();

timer.scheduleAtFixedRate(task, 0, delayTime);

}

public void stopTimer(){

if( task != null )

task.cancel();

isTimerRunning = false;

timer = null;

task = null;

}

//-----------------------------------------------------

class ProcessingRunner extends TimerTask

{

public void run()

{

if( isExit ) {

stopTimer();

app.notifyDestroyed();

}

if (!isTimerRunning || System.currentTimeMillis() -

scheduledExecutionTime() >= timerDelayTime)

{

return;

}

gameMain();

gameDraw();

repaint();

serviceRepaints();

System.gc();

}

}

//-------------------------------------------------

public GameCanvas(MIDlet midlet)

{

app = (PngFadeInOut)midlet;

}

public void start()

{

setFullScreenMode(true);

while (!isShown())

;

if( !isInited ) {

gameInit();

isInited = true;

}

startTimer(MAX_TARDINESS);

}

void gameInit()

{

scrW = getWidth();

scrH = getHeight();

if(g == null || offImage == null) {

offImage = Image.createImage(scrW, scrH);

g = offImage.getGraphics();

}

changeGameMode(gmStart);

}

public void changeGameMode(int gm){

gameMode = gm;

subMode = smInit;

}

//---------------------------------------------------

// 游戏主逻辑处理

//---------------------------------------------------

void gameMain()

{

if( gameMode == gmStart )

{

if( subMode == smInit )

{

// 取得图片的二进制数据

imgData = loadFile(imageName);

// 保存原始图片的调色板 rgb 数据

oldRGBData = getPlteRGBData(imgData);

if( fadeType == FADE_IN) {

// 设置调色板颜色为白色，淡入效果

for(int i = rgbDataStartPos; i < rgbDataStartPos + rgbDataLength;i++ ) {

imgData[i] = (byte)255;

}

}

// 生成新的图片

testImage = createFadeImage(imgData,rgbDataStartPos,rgbDataLength);

subMode = smProc ;

}

else if( subMode == smProc )

{

try {

// 淡入淡出效果处理

fade(fadeType);

testImage = createFadeImage(imgData,rgbDataStartPos,rgbDataLength);

}

catch ( Exception e ) {

println("Create fade image error. /n" + e);

}

}

}

}

//---------------------------------------------------

// 游戏描画处理

//---------------------------------------------------

protected void paint( Graphics _g){

if( offImage != null)

_g.drawImage(offImage, 0, 0, 0);

}

void gameDraw()

{

if( gameMode == gmStart )

{

if( subMode == smProc ){

g.setColor(0xffffff);

g.fillRect(0,0,scrW,scrH);

g.drawImage(testImage,20,140,0);

}

}

}

/**

* 淡入淡出效果处理

* @param type

*/

public void fade( int type)

{

int m = 0;

int n = 0;

// 淡入

if ( type == FADE_IN ) {

for( int i = 0; i < rgbDataLength; i++ )

{

m = imgData[rgbDataStartPos + i] & 0x000000ff;

n = oldRGBData[i] & 0x000000ff;

m = m < 0? m + 256 : m;

n = n < 0? n + 256 : n;

m = m > n ? m - FADE_STEP : n;

imgData[rgbDataStartPos + i] = (byte)(m & 0xff);

}

}

// 淡出

else if ( type == FADE_OUT ) {

for( int i = 0; i < rgbDataLength; i++ )

{

m = imgData[rgbDataStartPos + i] & 0x000000ff;

m = m < 0? m + 256 : m;

m = m < 255 ? m + FADE_STEP : 255;

imgData[rgbDataStartPos + i] = (byte)(m & 0xff);

}

}

}

/**

* 这里不是单纯创建一幅图片， crc32 校验码也在这个函数里更新

* @param data

* @param startPos 需要校验的数据的起始位置

* @return

*/

public Image createFadeImage(byte[] data,int startPos,int length)

{

if (crcTable == null)

makeCrcTable();

int endPos = startPos + length ;

int crc = updateCrcChunk( data, startPos -8,endPos );

data[endPos + 0] = (byte)(crc >> 24 & 0x000000FF);

data[endPos + 1] = (byte)(crc >> 16 & 0x000000FF);

data[endPos + 2] = (byte)(crc >> 8 & 0x000000FF);

data[endPos + 3] = (byte)(crc& 0x000000FF);

return Image.createImage(data,0,data.length);

}

static int rgbDataStartPos = 0;

static int rgbDataLength = 0;

/**

* @param imgData png 图片的二进制数据

* @return 调色板颜色数据的字节数组

*/

public byte[] getPlteRGBData(byte[] imgData)

{

if (imgData == null || imgData.length <= 1)

return null;

// PLTE chunk 数据域的类型标识

// see http://www.w3.org/TR/PNG/#11PLTE

String[] sPLTE = {"50", "4c", "54", "45"};

int i;

int pos = 0;

// 定位调色板数据的位置

for (i = 0; i < imgData.length; i++)

{

if (Integer.toHexString(imgData[i]).equals(sPLTE[0])

&& Integer.toHexString(imgData[i + 1]).equals(sPLTE[1])

&& Integer.toHexString(imgData[i + 2]).equals(sPLTE[2])

&& Integer.toHexString(imgData[i + 3]).equals(sPLTE[3]))

{

pos = i;

break;

}

}

pos -= 4;

// 取得 PLTE chunk 的字节数据长度 .

int imageNbColors = (

((imgData[pos] << 24) & 0xff000000)

| ((imgData[pos + 1] << 16) & 0x00ff0000)

| ((imgData[pos + 2] << 8 ) & 0x0000ff00)

| ((imgData[pos + 3] ) & 0x000000ff));

//8 = 数据长度 (4 个字节 ) + 类型标识 (4 个字节 )

pos += 8;

// 设置全局变量

rgbDataStartPos = pos;

rgbDataLength = imageNbColors;

// 复制数据

byte[] data = new byte[rgbDataLength ];

for( i = 0 ; i < rgbDataLength ; i++){

data[i] = imgData[i + rgbDataStartPos ];

}

return data;

}

// CRC 校验查找表，加速 CRC32 运算

static long crcTable[];

static public void makeCrcTable()

{

long c;

int n, k;

crcTable = new long[256];

for (n = 0; n < 256; n++) {

c = (long) n;

for (k = 0; k < 8; k++) {

if ((c & 1) == 1) {

c = 0xEDB88320L ^ (c >> 1);

}

else {

c = c >> 1;

}

}

crcTable[n] = c;

}

}

/**

* 计算 crc32 校验码

*/

static public int updateCrcChunk(byte[] buf, int dataOffsetStart,int dataOffsetEnd)

{

long c = 0xFFFFFFFFL;

for (int i = dataOffsetStart; i < dataOffsetEnd; i++)

c = (crcTable[(int) ((c ^ buf[i]) & 0xFF)] ^ (c >> 8));

return (int) (c ^ 0xFFFFFFFFL);

}

/**

* 读取文件的二进制数据

* @param fileName 文件名

* @return 文件二进制数据

*/

byte[] loadFile(String fileName)

{

DataInputStream isr = null;

byte[] bData;

try {

try {

isr = new DataInputStream(getClass().getResourceAsStream(fileName));

}

catch (Exception e) {

}

int res_size = 0;

while (isr.read() != -1)

res_size++;

if (isr.markSupported())

isr.reset();

else {

isr.close();

isr = new DataInputStream(getClass().getResourceAsStream(fileName));

}

bData = new byte[res_size];

int read_bytes = isr.read(bData, 0, res_size);

isr.close();

System.gc();

return bData;

}

catch (Exception e) {

println("Error>>loadFile " + fileName);

return null;

}

}

static void println(String str){

System.out.println( str );

}

}

----------------------CODE__END-------------------------------