在MIDP2.0中操作图片像素
作者:chenyi 文章来源:chenyis blog
正文
我们知道,在MIDP1.0中,除非我们利用特定厂商的API(比如Nokia),我们是没法对图片的像素进行操作的,但是在MIDP2.0中,Image和Graphics的功能都大大增强了。比如,我们可以获取Image的所有像素值,然后利用程序来修改这些像素(比如说ARGB各自的值),最后再把修改后的像素图绘制出来。通过直接操作图片像素,我们就获得了一种很强大的能力,用编程的方式实现出很多有趣的效果来,而不用额外制作新图片。比如说透明度渐变,颜色反转等。下面就是2个例子,分别实现透明度渐变和颜色反转的功能。
例题一:透明度渐变效果的实现
给定一张图片,假如我们想实现这么一种效果:图片由全透明状态逐渐清晰,最后达到正常状态。要实现这一个过程,我们首先要获取该图片的所有像素值,逐步让这些像素的alpha值从0转变到正常,每改变图片的所有像素值一次,我们就请求刷屏一次,把最新的像素图画出来,这样我们就能实现透明度渐变的效果了。代码实现如下:
- importjava.io.IOException;
- importjavax.microedition.lcdui.Canvas;
- importjavax.microedition.lcdui.Display;
- importjavax.microedition.lcdui.Graphics;
- importjavax.microedition.lcdui.Image;
- importjavax.microedition.midlet.MIDlet;
- importjavax.microedition.midlet.MIDletStateChangeException;
- /**
- *
- *@authorJagie
- *
- */
- publicclassShadowMIDletextendsMIDlet{
- Canvasc=newShadowCanvas();
- publicShadowMIDlet(){
- }
- protectedvoidstartApp()throwsMIDletStateChangeException{
- Display.getDisplay(this).setCurrent(c);
- }
- protectedvoidpauseApp(){
- //TODOAuto-generatedmethodstub
- }
- protectedvoiddestroyApp(booleanarg0)throwsMIDletStateChangeException{
- //TODOAuto-generatedmethodstub
- }
- }
- /**
- *
- *@authorJagie
- *
- */
- classShadowCanvasextendsCanvasimplementsRunnable{
- intw,h;
- //原始图片
- ImagesrcImage;
- //原始图片的像素数组
- int[]srcRgbImage;
- //渐变图片的像素数组
- int[]shadowRgbImage;
- intimgWidth,imgHeight;
- intcount;
- publicShadowCanvas(){
- w=this.getWidth();
- h=this.getHeight();
- try{
- srcImage=Image.createImage("/av.png");
- }catch(IOExceptione){
- //TODOAuto-generatedcatchblock
- e.printStackTrace();
- }
- imgWidth=srcImage.getWidth();
- imgHeight=srcImage.getHeight();
- //制造原始图片的像素数组,用一个int来代表每一个像素,按位表示方式是:0xAARRGGBB
- srcRgbImage=newint[imgWidth*imgHeight];
- //获取原始图片的所有像素,参见MIDPAPPI文档
- srcImage.getRGB(srcRgbImage,0,imgWidth,0,0,imgWidth,imgHeight);
- shadowRgbImage=newint[srcRgbImage.length];
- System.arraycopy(srcRgbImage,0,shadowRgbImage,0,
- shadowRgbImage.length);
- //渐变图片的所有像素已开始都是全透明的
- for(inti=0;i<shadowRgbImage.length;i++){
- shadowRgbImage[i]&=0x00ffffff;
- }
- newThread(this).start();
- }
- publicvoidpaint(Graphicsg){
- g.setColor(0,0,0);
- g.fillRect(0,0,w,h);
- //绘制渐变图片
- g.drawRGB(shadowRgbImage,0,imgWidth,(w-imgWidth)/2,
- (h-imgHeight)/2,imgWidth,imgHeight,true);
- g.setColor(0,255,0);
- g.drawString("count="+count,w/2,30,Graphics.HCENTER
- |Graphics.TOP);
- }
- publicvoidrun(){
- while(true){
- booleanchanged=false;
- //改变渐变图片的每一个像素
- for(inti=0;i<shadowRgbImage.length;i++){
- //获取渐变图片的某一像素的alpha值
- intalpha=(shadowRgbImage[i]&0xff000000)>>>24;
- //原始图片的对应像素的alpha值
- intoldAlpha=(srcRgbImage[i]&0xff000000)>>>24;
- if(alpha<oldAlpha){
- //alpha值++
- shadowRgbImage[i]=((alpha+1)<<24)
- |(shadowRgbImage[i]&0x00ffffff);
- changed=true;
- }
- }
- try{
- Thread.sleep(10);
- }catch(InterruptedExceptione){
- //TODOAuto-generatedcatchblock
- e.printStackTrace();
- }
- count++;
- repaint();
- //当所有像素的alpha值都达到原始值后,线程运行结束
- if(!changed){
- System.out.println("over");
- break;
- }
- }
- }
- }
透明度渐变效果如下:
例题二:颜色反转
在手机游戏中,我们经常会碰上这样一种情况,比如我方飞机和敌方飞机外观是完全一样的,唯一的区别就是颜色不同,比如说敌方飞机是红色的,而我方飞机是绿色的。在MIDP1.0中,我们就只好制作2张图片来表示2种飞机,自然,这样会造成jar空间的极大浪费。但是在MIDP2.0中,通过对图片直接进行像素操作,反转RGB中的一个值,我们只需要一张图片就够了,样例代码如下:
ColorMIDlet.java
- importjava.io.IOException;
- importjavax.microedition.lcdui.Canvas;
- importjavax.microedition.lcdui.Display;
- importjavax.microedition.lcdui.Graphics;
- importjavax.microedition.lcdui.Image;
- importjavax.microedition.midlet.MIDlet;
- importjavax.microedition.midlet.MIDletStateChangeException;
- /**
- *
- *@authorJagie
- *
- */
- publicclassColorMIDletextendsMIDlet{
- Canvasc=newColorCanvas();
- publicColorMIDlet(){
- super();
- //TODOAuto-generatedconstructorstub
- }
- protectedvoidstartApp()throwsMIDletStateChangeException{
- Display.getDisplay(this).setCurrent(c);
- }
- protectedvoidpauseApp(){
- //TODOAuto-generatedmethodstub
- }
- protectedvoiddestroyApp(booleanarg0)throwsMIDletStateChangeException{
- //TODOAuto-generatedmethodstub
- }
- }
- /**
- *
- *@authorJagie
- *
- */
- classColorCanvasextendsCanvas{
- ImagesrcImage;
- int[]targetImage1;
- int[]targetImage2;
- publicColorCanvas(){
- try{
- srcImage=Image.createImage("/av.png");
- }catch(IOExceptione){
- //TODOAuto-generatedcatchblock
- e.printStackTrace();
- }
- targetImage1=GraphicsUtil.flipImageColor(srcImage,
- GraphicsUtil.SHIFT_RED_TO_BLUE);
- targetImage2=GraphicsUtil.flipImageColor(srcImage,
- GraphicsUtil.SHIFT_RED_TO_GREEN);
- }
- publicvoidpaint(Graphicsg){
- g.setColor(0,0,0);
- g.fillRect(0,0,this.getWidth(),this.getHeight());
- g.setColor(0x00ff00);
- g.drawString("origin:",getWidth()/2,0,Graphics.TOP
- |Graphics.HCENTER);
- g.drawImage(srcImage,30,20,Graphics.LEFT|Graphics.TOP);
- g.drawString("SHIFT_RED_TO_BLUE:",getWidth()/2,
- srcImage.getHeight()+20,Graphics.TOP|Graphics.HCENTER);
- g.drawRGB(targetImage1,0,srcImage.getWidth(),30,srcImage
- .getHeight()+40,srcImage.getWidth(),srcImage.getHeight(),
- true);
- g.drawString("SHIFT_RED_TO_GREEN:",getWidth()/2,srcImage
- .getHeight()*2+40,Graphics.TOP|Graphics.HCENTER);
- g.drawRGB(targetImage2,0,srcImage.getWidth(),30,srcImage
- .getHeight()*2+60,srcImage.getWidth(),srcImage
- .getHeight(),true);
- }
- }
GraphicsUtil.java
- importjavax.microedition.lcdui.Image;
- /**
- *
- *@authorJagie
- *
- */
- publicclassGraphicsUtil{
- publicstaticfinalintSHIFT_RED_TO_GREEN=0;
- publicstaticfinalintSHIFT_RED_TO_BLUE=1;
- publicstaticfinalintSHIFT_GREEN_TO_BLUE=2;
- publicstaticfinalintSHIFT_GREEN_TO_RED=3;
- publicstaticfinalintSHIFT_BLUE_TO_RED=4;
- publicstaticfinalintSHIFT_BLUE_TO_GREEN=5;
- publicstaticint[]flipImageColor(Imagesource,intshiftType){
- //westartbygettingtheimagedataintoanintarray-thenumber
- //of32-bitintsisequaltothewidthmultipliedbytheheight
- int[]rgbData=newint[(source.getWidth()*source.getHeight())];
- source.getRGB(rgbData,0,source.getWidth(),0,0,source.getWidth(),
- source.getHeight());
- //nowgothrougheverypixelandadjustit'scolor
- for(inti=0;i<rgbData.length;i++){
- intp=rgbData[i];
- //splitoutthedifferentbytecomponentsofthepixelby
- //applying
- //amasksoweonlygetwhatweneed,thenshiftittomakeit
- //anormalnumberwecanplayaroundwith
- inta=((p&0xff000000)>>24);
- intr=((p&0x00ff0000)>>16);
- intg=((p&0x0000ff00)>>8);
- intb=((p&0x000000ff)>>0);
- intba=a,br=r,bb=b,bg=g;//backupcopies
- //flipthecolorsaroundaccordingtotheoperationrequired
- switch(shiftType){
- caseSHIFT_RED_TO_GREEN:
- g=r;
- r=bg;
- break;
- caseSHIFT_RED_TO_BLUE:
- b=r;
- r=bb;
- break;
- caseSHIFT_GREEN_TO_BLUE:
- g=b;
- b=bg;
- break;
- caseSHIFT_GREEN_TO_RED:
- g=r;
- r=bg;
- break;
- caseSHIFT_BLUE_TO_RED:
- b=r;
- r=bb;
- break;
- caseSHIFT_BLUE_TO_GREEN:
- b=g;
- g=bb;
- break;
- }
- //shiftallourvaluesbackin
- rgbData[i]=(a<<24)|(r<<16)|(g<<8)|b;
- }
- returnrgbData;
- }
- }