Android学习笔记_66_图片处理专题
1、图片缩放：不解析整个图片信息。
public class DemoActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ImageView iv = (ImageView) this.findViewById(R.id.iv);
// BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
// //按1/8的大小加载到内存
// bmpFactoryOptions.inSampleSize = 8;
// Bitmap bm = BitmapFactory.decodeFile("/sdcard/img.jpg",bmpFactoryOptions);
// iv.setImageBitmap(bm);
//
//1. 首先得到屏幕的宽高
Display currentDisplay = getWindowManager().getDefaultDisplay();
int dw = currentDisplay.getWidth();
int dh = currentDisplay.getHeight();
// 2. 获取图片的宽度和高度
BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
// 设置inJustDecodeBounds = true ,只会解析文件头信息;
bmpFactoryOptions.inJustDecodeBounds = true;
// 不会真正的解析这个位图
Bitmap bmp = BitmapFactory.decodeFile("/sdcard/img.jpg", bmpFactoryOptions);
//得到图片的宽度和高度
int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh);
int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw);
Log.v("HEIGHTRATIO",""+heightRatio);
Log.v("WIDTHRATIO",""+widthRatio);
//真正的解析位图
bmpFactoryOptions.inJustDecodeBounds = false;
if(heightRatio>widthRatio){
bmpFactoryOptions.inSampleSize = heightRatio;
}else{
bmpFactoryOptions.inSampleSize = widthRatio;
}
bmp = BitmapFactory.decodeFile("/sdcard/img.jpg", bmpFactoryOptions);
iv.setImageBitmap(bmp);
}
}
2、ExifInterface获取或设置图片的exif信息：
public class DemoActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try {
ExifInterface exif = new ExifInterface("sdcard/img.jpg");
System.out.println( exif.getAttribute(ExifInterface.TAG_DATETIME));
System.out.println( exif.getAttribute(ExifInterface.TAG_IMAGE_LENGTH));
System.out.println( exif.getAttribute(ExifInterface.TAG_IMAGE_WIDTH));
exif.setAttribute("camera", "柯达相机");
System.out.println( exif.getAttribute("camera"));
} catch (Exception e) {
e.printStackTrace();
}
}
}
3、从图库里面选择一个图片，然后将它设置到ImageView。
public class DemoActivity extends Activity {
ImageView iv;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
iv = (ImageView) this.findViewById(R.id.iv);
}
public void click(View view){
//选择图库意图，打开图库
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, 0);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if(data!=null){
//图片的uri
Uri uri = data.getData() ;
iv.setImageURI(uri);
}
super.onActivityResult(requestCode, resultCode, data);
}
}
4、创建图片（bitmap）的拷贝：
public class DemoActivity extends Activity{
ImageView iv1;
ImageView iv2;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
iv1= (ImageView) this.findViewById(R.id.iv1);
iv2= (ImageView) this.findViewById(R.id.iv2);
}
public void click(View view){
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, 0);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if(data!=null){
//图片的uri
Uri uri = data.getData() ;
iv1.setImageURI(uri);
// 获取第一个图片 的拷贝 设置到iv2的控件里面
try {
//通过uri获取一个流对象。getContentResolver().openInputStream(uri)
Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
//图片缩放
Matrix matrix = new Matrix();
// matrix.setValues(new float[] {
// 2, 0, 0,
// 0, 1, 0,
// 0, 0, 1
// });//矩阵缩放
// matrix.setScale(1.5f, 1.0f);//水平方向为1.5倍，垂直方向不做改变
// matrix.postTranslate(bitmap.getWidth(), 1.0f);//与setScale可以实现图片翻转
// matrix.setRotate(30);
//画笔
Paint paint = new Paint();
paint.setAntiAlias(true);//消除锯齿
matrix.setRotate(15);//图片旋转
//得到一个大小 配置跟原图一样的空白的位图
//Bitmap alterbitmap = Bitmap.createBitmap(bitmap.getWidth()*2, bitmap.getHeight(), bitmap.getConfig());
Bitmap alteredBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(),
matrix, false);
//画布对象
Canvas canvas = new Canvas();
//将图片流bitmap应用到画布上
canvas.drawBitmap(bitmap, matrix, paint);
iv2.setImageBitmap(alteredBitmap);
} catch (Exception e) {
e.printStackTrace();
}
}
super.onActivityResult(requestCode, resultCode, data);
}
}
最后一个：filter解释
true if the source should be filtered. Only applies if the matrix contains more than just translation.
当进行的不只是平移变换时，filter参数为true可以进行滤波处理，有助于改善新图像质量;flase时，计算机不做过滤处理。
图片裁剪，可用这个方法：
Bitmap source：要从中截图的原始位图
int x: 起始x坐标
int y：起始y坐标
int width： 要截的图的宽度
int height：要截的图的高度
要想imageView.setImageMatrix()方法起作用，xml得配置android:scaleType="matrix"
matrix.setRotate和matrix.postRotate的区别：
post...：平移、旋转等效果可以叠加在一起；
set...：前一种效果会消失，只有后来的操作，即它会重置Matrix
5、图片合成：
public class DemoActivity extends Activity {
Bitmap basebitmap;
Canvas canvas ;
Paint paint;
ImageView iv;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
iv = (ImageView) this.findViewById(R.id.iv);
}
public void select1(View view){
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, 10);
// 从图库里面获取第一个图片
}
public void save(View view){
File file = new File("/sdcard/1.jpg");
FileOutputStream fos;
try {
fos = new FileOutputStream(file);
basebitmap.compress(CompressFormat.JPEG, 100, fos);
//显示的发送一条广播
//sd卡挂载的广播
Intent intent = new Intent(Intent.ACTION_MEDIA_MOUNTED,Uri.parse("file://"+Environment.getExternalStorageDirectory()));
sendBroadcast(intent);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public void select2(View view){
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, 20);
// 从图库里面获取第一个图片
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if(requestCode==10){
if(data!=null){
Uri uri = data.getData();
try {
Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
basebitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());
canvas = new Canvas(basebitmap);
paint = new Paint();
canvas.drawBitmap(bitmap, 0, 0, paint);
} catch (Exception e) {
e.printStackTrace();
}
}
}else if(requestCode==20){
if(data!=null){
Uri uri = data.getData();
//把第二张位图的内容 画在 basebitmap上
try {
Bitmap bitmap = BitmapFactory.decodeStream( getContentResolver().openInputStream(uri));
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.MULTIPLY));
canvas.drawBitmap(bitmap, 0,0, paint);
iv.setImageBitmap(basebitmap);
} catch (Exception e) {
e.printStackTrace();
}
}
}
super.onActivityResult(requestCode, resultCode, data);
}
}
6、根据路径Path绘制文字：
public class DemoActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new MyView(this));
}
private class MyView extends View{
public MyView(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setTextSize(20);
paint.setTypeface(Typeface.DEFAULT);
Path p = new Path();
p.moveTo(20, 20);
p.lineTo(100, 150);
p.lineTo(200, 220);
canvas.drawTextOnPath("Hello this is text on a path", p, 0, 0, paint);
super.onDraw(canvas);
}
}
}
7、绘图（根据手指移动创建图片并保存）：
public class DemoActivity extends Activity {
ImageView iv;
Bitmap bitmap;
Canvas canvas;
Paint paint;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
iv = (ImageView) this.findViewById(R.id.iv);
Display diaplay = getWindow().getWindowManager().getDefaultDisplay();
int height = diaplay.getHeight() - 40;
int width = diaplay.getWidth();
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
iv.setImageBitmap(bitmap);
canvas = new Canvas(bitmap);
paint= new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(10);
iv.setOnTouchListener(new OnTouchListener() {
float startx = 0;
float starty = 0;
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startx = event.getX();
starty = event.getY();
break;
case MotionEvent.ACTION_MOVE:
float x = event.getX();
float y = event.getY();
canvas.drawLine(startx, starty, x, y, paint);
startx = event.getX();
starty = event.getY();
//通知imageview更新界面
iv.invalidate();
break;
case MotionEvent.ACTION_UP:
float endx = event.getX();
float endy = event.getY();
canvas.drawLine(startx, starty, endx, endy, paint);
//通知imageview更新界面
iv.invalidate();
break;
default:
break;
}
return true;
}
});
}
public void save(View view) {
File file = new File("/sdcard/"+System.currentTimeMillis()+".jpg");
FileOutputStream fos;
try {
fos = new FileOutputStream(file);
bitmap.compress(CompressFormat.JPEG, 100, fos);
//显示的发送一条广播
//sd卡挂载的广播
Intent intent = new Intent(Intent.ACTION_MEDIA_MOUNTED,Uri.parse("file://"+Environment.getExternalStorageDirectory()));
sendBroadcast(intent);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
8、矩阵Matrix
Matrix的操作，总共分为translate（平移），rotate（旋转），scale（缩放）和skew（倾斜）四种，每一种变换在Android的API里都提供了set, post和pre三种操作方式,除了translate，其他三种操作都可以指定中心点。 set是直接设置Matrix的值，每次set一次，整个Matrix的数组都会变掉。 post是后乘，当前的矩阵乘以参数给出的矩阵。可以连续多次使用post，来完成所需的整个变换。
例如，要将一个图片旋转30度，然后平移到(100,100)的地方，那么可以这样做:
Matrix m = new Matrix(); m.postRotate(30 ); m.postTranslate(100 , 100 );
pre是前乘，参数给出的矩阵乘以当前的矩阵。所以操作是在当前矩阵的最前面发生的。例如上面的例子，如果用pre的话
Matrix m = new Matrix(); m.setTranslate(100 , 100 ); m.preRotate(30 )
旋转、缩放和倾斜都可以围绕一个中心点来进行，如果不指定，默认情况下，是围绕(0,0)点来进行。
public class MyView extends View {
private Bitmap mBitmap;
private Matrix mMatrix = new Matrix();
public MyView(Context context) {
super (context);
initialize();
}
private void initialize() {
Bitmap bmp = ((BitmapDrawable)getResources().getDrawable(R.drawable.show)).getBitmap();
mBitmap = bmp;
/*首先，将缩放为100*100。这里scale的参数是比例。有一点要注意，如果直接用100/
bmp.getWidth()的话，会得到0，因为是整型相除，所以必须其中有一个是float型的，直接用100f就好。*/
mMatrix.setScale(100f/bmp.getWidth(), 100f/bmp.getHeight());
//平移到（100，100）处
mMatrix.postTranslate(100 , 100 );
//倾斜x和y轴，以（100，100）为中心。
mMatrix.postSkew(0 .2f, 0 .2f, 100 , 100 );
}
@Override protected void onDraw(Canvas canvas) {
// super.onDraw(canvas); //如果界面上还有其他元素需要绘制，只需要将这句话写上就行了。
canvas.drawBitmap(mBitmap, mMatrix, null );
}
}
pre方法表示矩阵前乘，例如：变换矩阵为A，原始矩阵为B，pre方法的含义即是A*B post方法表示矩阵后乘，例如：变换矩阵为A，原始矩阵为B，post方法的含义即是B*A matrix.preScale(0.5f, 1); matrix.preTranslate(10, 0); matrix.postScale(0.7f, 1); matrix.postTranslate(15, 0); 等价于： translate(10, 0) -> scale(0.5f, 1) -> scale(0.7f, 1) -> translate(15, 0) 注意：后调用的pre操作先执行，而后调用的post操作则后执行。 set方法一旦调用即会清空之前matrix中的所有变换，例如： matrix.preScale(0.5f, 1); matrix.setScale(1, 0.6f); matrix.postScale(0.7f, 1); matrix.preTranslate(15, 0); 等价于 translate(15, 0) -> scale(1, 0.6f) -> scale(0.7f, 1) matrix.preScale (0.5f, 1)将不起作用。
别人怎么说，怎么做，没办法的事，我自己要明白该怎么办。
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