Android 中 Bitmap 常用操作

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最新推荐文章于 2023-04-23 00:19:25 发布

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本文介绍了一个Android中的Bitmap处理工具类，包含读取、保存、裁剪、旋转、缩放等实用功能。通过示例展示了如何合并多个Bitmap，以及在Bitmap上进行绘图和文字标注的方法。

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Android 中 Bitmap 常用操作

一些Bitmap常用操作写到一个工具类里：读取，保存，裁剪，旋转，缩放，绘制，写字

package com.example.wurui.jnitest;

import android.app.Application;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;

/**
 * Created by wurui on 17-12-29.
 */

public class BitmapProcess {

    // 读取Bitmap
    public Bitmap readFromSdcard(){
        Bitmap testbitmap = null;
        try {
            File file1 = new File("/storage/emulated/0/Android/"+"image.jpg");
            InputStream in = new FileInputStream(file1);
            testbitmap = BitmapFactory.decodeStream(in).copy(Bitmap.Config.ARGB_8888, true);
            // 不允许对drawable的文件修改，canvas会报错，要拷贝;
        }catch (Exception e){
        }
        return testbitmap;
    }

    public Bitmap readFromAssets(String filename){
        Bitmap testbitmap = null;
        try{
            filename = "test/golf299.jpg"; // Assets/test/golf299.jpg
            InputStream stream =  MyApplication.getMyApplication().getApplicationContext().getAssets().open(filename);
            testbitmap = BitmapFactory.decodeStream(stream);
        }
        catch (Exception e){
        }
        return testbitmap;
    }

    // 裁剪Bitmap
    public Bitmap cutBitmap(Bitmap bmp, int w, int h){
        return Bitmap.createScaledBitmap(bmp, w, h,true);
    }

    // 多张Bitmap融合贴片： 示例4张合并
    private Bitmap mergeBitmap(Bitmap m1, Bitmap m2,Bitmap m3,Bitmap m4){
        int scaled_size = (int) m1.getHeight()/2;
        Bitmap map1 = Bitmap.createScaledBitmap(m1,scaled_size,scaled_size,true);
        Bitmap map2 = Bitmap.createScaledBitmap(m2,scaled_size,scaled_size,true);
        Bitmap map3 = Bitmap.createScaledBitmap(m3,scaled_size,scaled_size,true);
        Bitmap map4 = Bitmap.createScaledBitmap(m4,scaled_size,scaled_size,true);
        Bitmap map0 = Bitmap.createBitmap(m1.getWidth(),m1.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(map0);
        canvas.drawBitmap(map1,0,0,null);
        canvas.drawBitmap(map2,scaled_size,0,null);
        canvas.drawBitmap(map3,0,scaled_size,null);
        canvas.drawBitmap(map4,scaled_size,scaled_size,null);
        return map0;
    }

    // 旋转和缩放Bitmap
    public static Bitmap rotateResize(Bitmap bmp, int angle, int dw, int dh){
        int w = bmp.getWidth();
        int h = bmp.getHeight();
        float scaleW = ((float)dw) / w;
        float scaleH = ((float)dh) / h;
        Matrix matrix = new Matrix();
        matrix.postScale(scaleW,scaleH);
        matrix.postRotate(angle);
        bmp = Bitmap.createBitmap(bmp,0, 0, dw, dh, matrix, true);
        return bmp;
    }

    // 在Bitmap上画图和写字
    public void drawBitmap(Bitmap resource, int[] eigen) {
        Canvas canvas = new Canvas(resource);
        Paint paint = new Paint();
        paint.setColor(Color.GREEN);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(2);

        canvas.drawCircle(10, 20, 3, paint);
        canvas.drawLine(0, 0, 10, 10, paint);

        String text = " 一些字 ";
        Paint paintText = new Paint(Paint.ANTI_ALIAS_FLAG);
        paintText.setColor(Color.BLUE);
        paintText.setStyle(Paint.Style.STROKE);
        paintText.setStrokeWidth(2);
        canvas.drawText(text, 10, 40, paintText);
    }

    // 保存Bitmap到本地
    public boolean saveBitmapTofile(Bitmap bmp, String filename) {
        if (bmp == null || filename == null)
            return false;
        Bitmap.CompressFormat format = Bitmap.CompressFormat.JPEG;
        int quality = 100;
        FileOutputStream stream = null;
        try {
            stream = new FileOutputStream("/storage/emulated/0/Android/frames/" + filename);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return bmp.compress(format, quality, stream);
    }
}