理想情况下，我需要在我正在开发的Android应用上离线访问墨西哥地形海拔高度的信息。我下载了一个.bil文件，并用QGIS将其转换为.tif文件，结果文件差不多是900 MB。
我不知道它是否会起作用，我还在学习开发Android应用程序，但我打算将它存储在SD卡中，我想知道是否可以访问单个像素阅读整个图像，因为我知道这是不可能的。
有人可以告诉我是否有可能吗？如果是的话，该怎么做？或者获取我需要的信息的任何其他方式可能将.bil文件转换为其他格式或类似的东西。
感谢您的回答。
答案 0 :(得分：0)
Tiff将图像存储为以定义的偏移量开始的字节行。因此，您可以轻松检索单个像素，当然无需加载完整图像。 如果在十六进制编辑器中打开任何tif文件，您将看到前4个字节按代码标记tiff。接下来的4个字节为关于tif图像的元数据提供偏移量。 使用随机访问文件打开图像tif文件，然后寻找偏移量并进入元数据空间。从这里你可以选择所需像素的偏移量。然后去拿它......
我们只是为了这个目的。那就是访问各个像素。如果我们需要满载图像，那么jpeg或BMP就足够了。
答案 1 :(得分：0)
点击此链接查看完整代码： - full example to decode tiff image
package com.tif;
import android.os.*;import android.content.*;import android.app.*;import android.widget.*;import android.view.*;
import android.view.View.*;import android.graphics.*;import java.io.*;import java.util.*;import android.util.*;
import java.lang.*;import java.nio.*;import java.nio.channels.*;
public class Main extends Activity
{
private static final int CLEAR_CODE = 256;
private static final int EOI_CODE = 257;
long bytesCount=0L;
ScrollView sv;TextView tv;ImageView iv;
List intList;
long[] stripOffs,stripBytes;
byte[] bytes,ubytes,bmpBytes;
ByteBuffer bBuff;
BitBuffer bitBuff;
int entries,type,tag;
long count,value,ifd,stripAt,stripCount,stripBytesAt,rows,cols;
String txt="Null",path="",decompressed="";
String[] info= {"width","length","bitsPerSample","Compression","PhotometricInterpretation","FillOrder","StripOffsets","SamplesPerPixel","RowsPerStrip"
,"StripBytes","XResolution","YResolution","PlanarConfig","ResolutionUnit","extra","NextIFD"};
Bitmap bmp=null;
class DotsView extends View
{
int i = 0;Bitmap bmp;Canvas cnv;Rect bounds;Paint p;int width,height;
int alfa,red,green,blue;
public DotsView(Context context ,int width ,int height)
{
super(context);
this.width = width;
this.height = height;
bmp = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
cnv = new Canvas(bmp);
bounds = new Rect(0 , 0, width,height);
p = new Paint();
}
@Override
protected void onDraw(Canvas c)
{
for(int i=0;i<width;i++)
for(int j=0;j<height;j++)
{
for(int pix=0;pix<3;pix++)
{
if(pix==0)blue=bmpBytes[i+j+pix];
if(pix==1)green=bmpBytes[i+j+pix];
if(pix==2)red=bmpBytes[i+j+pix];
}
p.setColor( Color.argb(255, red,green,blue) );
cnv.drawPoint(i,j, p);
}
c.drawBitmap(bmp, null, bounds , null);
invalidate();
}
}
public int myShort(short sh)
{ int i;
ByteBuffer shortBuff=ByteBuffer.allocate(4);
shortBuff.order(ByteOrder.BIG_ENDIAN);shortBuff.putShort(sh);shortBuff.rewind();
shortBuff.order(ByteOrder.LITTLE_ENDIAN);sh=shortBuff.getShort();
if(sh<0)i=(int)(sh+32768); else i=(int)sh;
return i;
}
public long myInt(int i)
{ long l=0L;
ByteBuffer intBuff=ByteBuffer.allocate(4);
intBuff.order(ByteOrder.BIG_ENDIAN);intBuff.putInt(i);intBuff.rewind();
intBuff.order(ByteOrder.LITTLE_ENDIAN); i=intBuff.getInt();
if(i<0)l=(long)(i+2147483648L); else l=(long)i;
return l;
}
public String tagInfo(int tag)
{ int i=0;
switch(tag)
{case 256: i=0;break;case 257: i=1;break;case 258: i=2;break;case 259: i=3;break;case 262: i=4;break;case 266: i=5;break;
case 273: i=6;break;case 277: i=7;break;case 278: i=8;break;case 279: i=9;break;case 282: i=10;break;case 283: i=11;break;
case 284: i=12;break;case 296: i=13;break;case 1496: i=14;break;case 0: i=15;break;
}
return info[i];
}
public void extractTif()
{
String taginfo="";String strVal="";
FileInputStream fis;BufferedInputStream bis;DataInputStream dis;
path=Environment.getExternalStorageDirectory().getPath();
path=path+"/DCIM"+"/kpd.tif";
try {
fis=new FileInputStream(path);bis=new BufferedInputStream(fis);dis=new DataInputStream(bis);
dis.skip(4);ifd=myInt(dis.readInt());
txt="TIFF-IFD: "; txt=txt+ifd;
dis.skip(ifd-8); entries=myShort(dis.readShort());
txt=txt+"\nNo.OfEntries="+entries;
for(int i=0;i<=entries;i++)
{ tag=myShort( dis.readShort() );taginfo=tagInfo(tag);
type=myShort( dis.readShort() );count=myInt( dis.readInt() );value=myInt( dis.readInt() );
if(type==3)strVal="Value="; else strVal="Offset=";
if( strVal.equals("Offset=") )
{
if( taginfo.equals("StripOffsets") ){stripAt=value;stripCount=count;}
if( taginfo.equals("StripBytes") ){stripBytesAt=value;}
}
if( taginfo.equals("width") ){cols=value;}
if( taginfo.equals("length") ){rows=value;}
txt=txt+"\ntag="+tag+" "+tagInfo(tag)+",type="+type+",count="+count+strVal+value;
}
dis.close();bis.close();fis.close();
}catch(Exception e) {txt=txt+"\nerror="+e.toString();}
txt=txt+"\nNo.OfStrips="+stripCount+",array of strip locations at: "+stripAt+" and array of bytesPerStrip at "+stripBytesAt ;
extractBMP();
}
public void extractBMP()
{try{ File f=new File(path);RandomAccessFile raf=new RandomAccessFile(f,"r");
raf.seek(stripAt);stripOffs=new long[(int)stripCount];
txt=txt+"\nArray Of Image Offsets=";
for(int i=0;i<stripCount;i++){stripOffs[i]=myInt( raf.readInt() ); txt=txt+","+stripOffs[i]; }
raf.seek(stripBytesAt); stripBytes=new long[(int)stripCount];
txt=txt+"\nArray Of Strip Bytes =";
for(int i=0;i<stripCount;i++){stripBytes[i]=myInt(raf.readInt()); txt=txt+","+stripBytes[i];bytesCount+=stripBytes[i];}
txt=txt+stripBytes;
bBuff =ByteBuffer.allocate((int)(rows*cols*3));
for(int i=0;i<stripCount;i++)
{
bytes =new byte[(int)stripBytes[i]];
raf.seek(stripOffs[i]);
raf.read(bytes);
bBuff.put(lzwUncompress(bytes));
bytes=null;
}
txt=txt+"\nBuffered Image Bytes Size="+bBuff.position();
bBuff.rewind();
bmpBytes=new byte[bBuff.remaining()];
bmpBytes=bBuff.array();
txt=txt+"\nCount of bmpBytes="+bmpBytes.length;
bmp=BitmapFactory.decodeByteArray(bmpBytes,0,bmpBytes.length);
SystemClock.sleep(5000);
txt=txt+"Bitmap Object, bmp="+bmp;
if(bmp!=null){iv.setImageBitmap(bmp);sv.addView(iv);}
raf.close();
}catch(Exception e){txt=txt+"\nerror="+e.toString();}
}
public void lzw()
{
//String[] table=new String[4096];
byte b;char ch;String s;String pre="";short sh;
//List strTable=Arrays.asList(table);
//for(int i=0;i<255;i++)table[i]=Character.toString((char)i);
for(int i=0;i<100;i++)
{
b=bytes[i];
if(b<0)sh=(short)(128+b);
else sh=(short)b;
//ch=(char)b;
s=String.valueOf(sh);
//s=s+pre;
//if(strTable.contains(s)){pre=s;}
//else{ }
txt=txt+"Byte No."+i+"="+s+" ";
}
}
public void onCreate(Bundle bnd)
{
super.onCreate(bnd);
extractTif();
//sv=new ScrollView(this);
//tv=new TextView(this);
//iv=new ImageView(this);
//tv.setTextSize(7);
//sv.addView(tv);
//sv.addView(iv);
//tv.setText(txt);
//setContentView(sv);
Point res=new Point(); getWindowManager().getDefaultDisplay().getSize(res);
DotsView myView = new DotsView(this,res.x,res.y);
setContentView(myView);
}