Android中的二值化图像 [英] Binarize Image in Android
本文介绍了Android中的二值化图像的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在开发使用tesseract OCR扫描图像文本的Android应用程序，
我听说在对它执行OCR之前二值化图像会得到更好的结果，
所以我开始寻找执行操作的代码，
I am developing android app that uses tesseract OCR to scan a text from image,
I heard that binarizing image before performing OCR on it will give better result,
So I start looking for a code that do the operation,
我发现很少但它实际上在java中并且需要awt库...所以它们不适用于android。< br>
你能帮我找一个。
谢谢你
I found few but its actually in java and needs awt library ... so they don't work on android.
So can you help me to find one.
thank you
推荐答案
一个简单的解决方案
A Simple Solution
在下文中，我只是根据正常的三维方式改变图像中的每个像素 - 空间距离公式。我根据它们与这些颜色的距离来决定像素应该是黑色还是白色。例如，（1,2,3）更接近（0,0,0）而不是（255,255,255），因此它被确定为黑色。我确信那里有更聪明的算法。这只是一个简单的
In the following, I simply alter each pixel in an image based on the normal 3-dimension-space distance formula. I decide whether a pixel should be black or white based on how far it is from each of these colors. For example, (1,2,3) is closer to (0,0,0) than it is to (255,255,255) and therefore it is decided to be black. I'm sure there are more clever algorithms out there. This is just a simple one
MainActivity.java
package com.example.binarizeimage;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Environment;
import android.widget.ImageView;
import com.example.binarizeimage.R.drawable;
/**
* @author Sherif elKhatib - shush
*
*/
public class MainActivity extends Activity {
/**
* Boolean that tells me how to treat a transparent pixel (Should it be black?)
*/
private static final boolean TRASNPARENT_IS_BLACK = false;
/**
* This is a point that will break the space into Black or white
* In real words, if the distance between WHITE and BLACK is D;
* then we should be this percent far from WHITE to be in the black region.
* Example: If this value is 0.5, the space is equally split.
*/
private static final double SPACE_BREAKING_POINT = 13.0/30.0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//this is the original image
Bitmap theOriginalImage = BitmapFactory.decodeResource(this.getResources(), drawable.ic_launcher);
//this is the image that is binarized
Bitmap binarizedImage = convertToMutable(theOriginalImage);
// I will look at each pixel and use the function shouldBeBlack to decide
// whether to make it black or otherwise white
for(int i=0;i<binarizedImage.getWidth();i++) {
for(int c=0;c<binarizedImage.getHeight();c++) {
int pixel = binarizedImage.getPixel(i, c);
if(shouldBeBlack(pixel))
binarizedImage.setPixel(i, c, Color.BLACK);
else
binarizedImage.setPixel(i, c, Color.WHITE);
}
}
ImageView iv = (ImageView) findViewById(R.id.imageView1);
ImageView ivb = (ImageView) findViewById(R.id.ImageView01);
//show the original image
iv.setImageBitmap(BitmapFactory.decodeResource(this.getResources(), drawable.ic_launcher));
//show the binarized image
ivb.setImageBitmap(binarizedImage);
}
/**
* @param pixel the pixel that we need to decide on
* @return boolean indicating whether this pixel should be black
*/
private static boolean shouldBeBlack(int pixel) {
int alpha = Color.alpha(pixel);
int redValue = Color.red(pixel);
int blueValue = Color.blue(pixel);
int greenValue = Color.green(pixel);
if(alpha == 0x00) //if this pixel is transparent let me use TRASNPARENT_IS_BLACK
return TRASNPARENT_IS_BLACK;
// distance from the white extreme
double distanceFromWhite = Math.sqrt(Math.pow(0xff - redValue, 2) + Math.pow(0xff - blueValue, 2) + Math.pow(0xff - greenValue, 2));
// distance from the black extreme //this should not be computed and might be as well a function of distanceFromWhite and the whole distance
double distanceFromBlack = Math.sqrt(Math.pow(0x00 - redValue, 2) + Math.pow(0x00 - blueValue, 2) + Math.pow(0x00 - greenValue, 2));
// distance between the extremes //this is a constant that should not be computed :p
double distance = distanceFromBlack + distanceFromWhite;
// distance between the extremes
return ((distanceFromWhite/distance)>SPACE_BREAKING_POINT);
}
/**
* @author Derzu
*
* @see http://stackoverflow.com/a/9194259/833622
*
* Converts a immutable bitmap to a mutable bitmap. This operation doesn't allocates
* more memory that there is already allocated.
*
* @param imgIn - Source image. It will be released, and should not be used more
* @return a copy of imgIn, but muttable.
*/
public static Bitmap convertToMutable(Bitmap imgIn) {
try {
//this is the file going to use temporally to save the bytes.
// This file will not be a image, it will store the raw image data.
File file = new File(Environment.getExternalStorageDirectory() + File.separator + "temp.tmp");
//Open an RandomAccessFile
//Make sure you have added uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
//into AndroidManifest.xml file
RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
// get the width and height of the source bitmap.
int width = imgIn.getWidth();
int height = imgIn.getHeight();
Config type = imgIn.getConfig();
//Copy the byte to the file
//Assume source bitmap loaded using options.inPreferredConfig = Config.ARGB_8888;
FileChannel channel = randomAccessFile.getChannel();
MappedByteBuffer map = channel.map(MapMode.READ_WRITE, 0, imgIn.getRowBytes()*height);
imgIn.copyPixelsToBuffer(map);
//recycle the source bitmap, this will be no longer used.
imgIn.recycle();
System.gc();// try to force the bytes from the imgIn to be released
//Create a new bitmap to load the bitmap again. Probably the memory will be available.
imgIn = Bitmap.createBitmap(width, height, type);
map.position(0);
//load it back from temporary
imgIn.copyPixelsFromBuffer(map);
//close the temporary file and channel , then delete that also
channel.close();
randomAccessFile.close();
// delete the temp file
file.delete();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return imgIn;
}
}
* activity_main.xml *
*activity_main.xml*
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView2"
android:layout_centerHorizontal="true"
android:text="Original Image" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView1"
android:layout_centerHorizontal="true"
android:src="@drawable/ic_launcher" />
<TextView
android:id="@+id/TextView02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/imageView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="28dp"
android:text="YES/NO Image" />
<ImageView
android:id="@+id/ImageView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/TextView02"
android:layout_centerHorizontal="true"
android:src="@drawable/ic_launcher" />
</RelativeLayout>
这篇关于Android中的二值化图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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