[Android] 使用Matrix矩阵类对图像进行缩放、旋转、对比度、亮度处理

    前一篇文章讲述了Android拍照、截图、保存并显示在ImageView控件中,该篇文章继续讲述Android图像处理技术,主要操作包括:通过打开相册里的图片,使用Matrix对图像进行缩放、旋转、移动、对比度、亮度、饱和度操作,希望对大家有所帮助.

一. 显示打开图片

    首先,设置activity_main.xml布局如下所示：

    然后,在Mainctivity.java中public class MainActivity extends Activity函数添加代码如下：

private Button selectBn;
private ImageView imageShow;
private ImageView imageCreate;
private TextView textview1;
private TextView textview2;
private Bitmap bmp; //原始图片

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    selectBn = (Button) findViewById(R.id.button1);
    imageShow = (ImageView) findViewById(R.id.imageView1);
    imageCreate = (ImageView) findViewById(R.id.imageView2);
    textview1 = (TextView) findViewById(R.id.textView1);
    textview2 = (TextView) findViewById(R.id.textView2);
    
    //选择图片
    selectBn.setOnClickListener(new OnClickListener() {
    	@Override
    	public void onClick(View v) {
    		Intent intent = new Intent(Intent.ACTION_PICK, 
    				android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    		startActivityForResult(intent, 0 );
    	}
    });
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }
}
//显示两张图片
protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
	super.onActivityResult(requestCode, resultCode, data);
	if(resultCode==RESULT_OK) {
		ShowPhotoByImageView(data);     //显示照片
		CreatePhotoByImageView();          //创建图片
	}
}

    再调用自定义函数实现显示图片：

//自定义函数 显示打开的照片在ImageView1中
public void ShowPhotoByImageView(Intent data) {
	Uri imageFileUri = data.getData();
	DisplayMetrics dm = new DisplayMetrics();
	getWindowManager().getDefaultDisplay().getMetrics(dm);
	int width = dm.widthPixels;    //手机屏幕水平分辨率
	int height = dm.heightPixels;  //手机屏幕垂直分辨率
	Log.v("height", ""+height );
	Log.v("width", ""+width);
	try {
		// Load up the image's dimensions not the image itself
		BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
		bmpFactoryOptions.inJustDecodeBounds = true;
		bmp = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageFileUri), null, bmpFactoryOptions);
		int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)height);
		int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)width);
		Log.v("bmpheight", ""+bmpFactoryOptions.outHeight);
		Log.v("bmpheight", ""+bmpFactoryOptions.outWidth);
		if(heightRatio>1&&widthRatio>1) {
			if(heightRatio>widthRatio) {
				bmpFactoryOptions.inSampleSize = heightRatio*2;
			}
			else {
				bmpFactoryOptions.inSampleSize = widthRatio*2;
			}
		}
		 //图像真正解码   
	    bmpFactoryOptions.inJustDecodeBounds = false;      		    
	    bmp = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageFileUri), null, bmpFactoryOptions);  
	    imageShow.setImageBitmap(bmp); //将剪裁后照片显示出来  
	    textview1.setVisibility(View.VISIBLE);
	} catch(FileNotFoundException e) {
		e.printStackTrace();
	}
}
//创建第二张图片并显示
public void CreatePhotoByImageView() {
	try {
	    Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
    	Canvas canvas = new Canvas(createBmp); //画布 传入位图用于绘制
    	Paint paint = new Paint(); //画刷 改变颜色 对比度等属性
    	canvas.drawBitmap(bmp, 0, 0, paint);    //错误:没有图片 因为参数bmp写成createBmp
    	imageCreate.setImageBitmap(createBmp);
    	textview2.setVisibility(View.VISIBLE);
	} catch(Exception e) {
		e.printStackTrace();
	}
}

    显示的效果如下图所示,该图叫莱娜图(Lenna),是图像处理中经常使用的样例图.

二. Matrix操作

   然后通过Matrix对图像进行处理操作,在onCreate函数中添加点击事件:

//缩小图片
Button button2=(Button)findViewById(R.id.button2);
button2.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		SmallPicture();
	}
});
//放大图片
    Button button3=(Button)findViewById(R.id.button3);
    button3.setOnClickListener(new OnClickListener() {
		@Override
		public void onClick(View v) {
			BigPicture();
		}
	});
   //旋转图片
Button button4=(Button)findViewById(R.id.button4);
button4.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		TurnPicture();
	}
});
//图片饱和度改变
Button button5=(Button)findViewById(R.id.button5);
button5.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		SaturationPicture();
	}
});
//图片对比度改变
Button button6=(Button)findViewById(R.id.button6);
button6.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		ContrastPicture();
	}
});

    最后分别自定义函数各操作实现,代码如下：

//缩小图片
private void SmallPicture() {
	Matrix matrix = new Matrix();
	//缩放区间 0.5-1.0
	if(smallbig>0.5f)
		smallbig=smallbig-0.1f;
	else
		smallbig=0.5f;
	//x y坐标同时缩放
	matrix.setScale(smallbig,smallbig,bmp.getWidth()/2,bmp.getHeight()/2); 
	Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
	Canvas canvas = new Canvas(createBmp); //画布 传入位图用于绘制
	Paint paint = new Paint(); //画刷 改变颜色 对比度等属性
    	canvas.drawBitmap(bmp, matrix, paint);
    	imageCreate.setBackgroundColor(Color.RED);
    	imageCreate.setImageBitmap(createBmp);
    	textview2.setVisibility(View.VISIBLE);
    }
  //放大图片
private void BigPicture() {
	Matrix matrix = new Matrix();
	//缩放区间 0.5-1.0
	if(smallbig<1.5f)
		smallbig=smallbig+0.1f;
	else
		smallbig=1.5f;
	//x y坐标同时缩放
	matrix.setScale(smallbig,smallbig,bmp.getWidth()/2,bmp.getHeight()/2); 
	Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
	Canvas canvas = new Canvas(createBmp); 
	Paint paint = new Paint(); 
	canvas.drawBitmap(bmp, matrix, paint);
	imageCreate.setBackgroundColor(Color.RED);
	imageCreate.setImageBitmap(createBmp);
	textview2.setVisibility(View.VISIBLE);
}
//旋转图片
private void TurnPicture() {
	Matrix matrix = new Matrix();
	turnRotate=turnRotate+15;
	//选择角度 饶(0,0)点选择 正数顺时针 负数逆时针 中心旋转
	matrix.setRotate(turnRotate,bmp.getWidth()/2,bmp.getHeight()/2); 
	Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
	Canvas canvas = new Canvas(createBmp); 
	Paint paint = new Paint(); 
	canvas.drawBitmap(bmp, matrix, paint);
	imageCreate.setBackgroundColor(Color.RED);
	imageCreate.setImageBitmap(createBmp);
	textview2.setVisibility(View.VISIBLE);
}
//改变图像饱和度
private void SaturationPicture() {
	//设置饱和度 0表示灰度图像 大于1饱和度增加 0-1饱和度减小
	ColorMatrix cm = new ColorMatrix();
	cm.setSaturation(saturation);
	Paint paint = new Paint(); 
	paint.setColorFilter(new ColorMatrixColorFilter(cm));
	//显示图片
	Matrix matrix = new Matrix();
	Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
	Canvas canvas = new Canvas(createBmp); 
	canvas.drawBitmap(bmp, matrix, paint);
	imageCreate.setImageBitmap(createBmp);
	textview2.setVisibility(View.VISIBLE);
	saturation=saturation+0.1f;
	if(saturation>=1.5f) {
		saturation=0f;
	}
}
//设置图片对比度
private void ContrastPicture() {
	ColorMatrix cm = new ColorMatrix();
	float brightness = -25;  //亮度
	float contrast = 2;        //对比度
	cm.set(new float[] {
		contrast, 0, 0, 0, brightness,
		0, contrast, 0, 0, brightness,
		0, 0, contrast, 0, brightness,
		0, 0, 0, contrast, 0
	});
	Paint paint = new Paint(); 
	paint.setColorFilter(new ColorMatrixColorFilter(cm));
	//显示图片
	Matrix matrix = new Matrix();
	Bitmap createBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
	Canvas canvas = new Canvas(createBmp); 
	canvas.drawBitmap(bmp, matrix, paint);
	imageCreate.setImageBitmap(createBmp);
	textview2.setVisibility(View.VISIBLE);
}

    同时自定义变量如下：

//图片变换参数
private float smallbig=1.0f;   //缩放比例
private int turnRotate=0;       //旋转度数
private float saturation=0f;    //饱和度

    它的运行结果如下图所示：
   
   
   
    需要指出的是：该项目仅仅讲述处理的过程,并没有考虑很多因素,如:有的图像显示可能超出屏幕,没有载入图片点击处理按钮报错,横竖屏切换导致不显示图片,最下面按钮可能被遮挡,图像放大画布没有变,因为为认为显示一张改变后的图片效果更好,而该工程仅仅是对比.图像缩放移动触屏变换更好,下一篇讲述.
    XML布局推荐：http://www.apkbus.com/forum.php?mod=viewthread&tid=44949
    解决画布跟着图片放大：http://www.eoeandroid.com/thread-3162-1-1.html

三. Matrix处理的原理

    Android中可以通过Matrix和ColorMatrix对图像进行处理.
    1.Matrix
    图像空间变换,包括旋转、剪裁、缩放或移动.Matrix类中每个数字都将应用于图像上每个点的3个坐标x\y\z之一.
    如下代码通过setValues设置值.(1,0,0)表示x坐标转换x=1x+0y+0z,同样y=0x+1y+0z,z=0x+0y+1z.该矩阵不做任何变换.如果第一行改为(.5f,0,0),那么图像在x轴上将图像压缩50%.移动见setTranslate()函数.

Matrix matrix = new Matrix();
matrix.setValues(new float[] {
        1, 0, 0,
        0, 1, 0,
        0, 0, 1
});

    2.ColorMatrix
    在Canvas(画布)对象上绘制时既可使用Matrix方法,也可使用ColorMatrix来改变在Canvas对象上绘制的Paint(画刷)对象.对图像的像素处理时,每个像素由RGBA值组成(Red Green Blue Alpha).具体方法推荐博文:http://www.cnblogs.com/leon19870907/articles/1978065.html
    最后希望该文章对大家有所帮助,尤其是Android初学者.该文章是讲述Android使用Matrix处理图片的基础文章,如果有不足或错误地方,请见谅~参考资料《Android多媒体开发高级编程 著：Shawn Van Every》
    下载地址:http://download.csdn.net/detail/eastmount/8082043
(By:Eastmount 2014-10-26 夜2点 http://blog.csdn.net/eastmount)