Android 图片压缩的几种方法

当图片太大不满足需求时，需要对图片进行裁剪压缩处理，常用的压缩处理接口主要有三种：质量压缩法，尺寸压缩法，缩略图压缩法和等比例压缩法，具体代码如下：

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.media.ThumbnailUtils;
import android.util.Log;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;


public class BitmapUtils {

    
    static private Bitmap compressImage(Bitmap beforeBitmap) {

        // 可以捕获内存缓冲区的数据，转换成字节数组。
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        if (beforeBitmap != null) {
            // 第一个参数：图片压缩的格式；第二个参数：压缩的比率；第三个参数：压缩的数据存放到bos中
            beforeBitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);
            
            // 循环判断压缩后的图片大小是否满足要求，这里限制100kb，若不满足则继续压缩，每次递减10%压缩
            int options = 100;
            while (bos.toByteArray().length / 1024 > 100) {
                bos.reset();// 置为空
                beforeBitmap.compress(Bitmap.CompressFormat.JPEG, options, bos);
                options -= 10;
            }
            
            // 从bos中将数据读出来 转换成图片
            ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
            Bitmap afterBitmap = BitmapFactory.decodeStream(bis);
            return afterBitmap;
        }
        return null;
    }

    
    static public Bitmap getThumbnail(Bitmap beforeBitmap, int width, int height) {
        return ThumbnailUtils.extractThumbnail(beforeBitmap, width, height);
    }

    
    static public Bitmap compressBitmap1(Bitmap beforeBitmap, double newWidth, double newHeight) {
        // 图片原有的宽度和高度
        float beforeWidth = beforeBitmap.getWidth();
        float beforeHeight = beforeBitmap.getHeight();

        // 计算宽高缩放率
        float scaleWidth = 0;
        float scaleHeight = 0;
        if (beforeWidth > beforeHeight) {
            scaleWidth = ((float) newWidth) / beforeWidth;
            scaleHeight = ((float) newHeight) / beforeHeight;
        } else {
            scaleWidth = ((float) newWidth) / beforeHeight;
            scaleHeight = ((float) newHeight) / beforeWidth;
        }

        // 矩阵对象
        Matrix matrix = new Matrix();
        // 缩放图片动作 缩放比例
        matrix.postScale(scaleWidth, scaleHeight);
        // 创建一个新的Bitmap 从原始图像剪切图像
        Bitmap afterBitmap = Bitmap.createBitmap(beforeBitmap, 0, 0,
                (int) beforeWidth, (int) beforeHeight, matrix, true);
        return afterBitmap;
    }

    
    static public Bitmap compressBitmap(Bitmap beforBitmap, double maxWidth, double maxHeight) {

        // 图片原有的宽度和高度
        float beforeWidth = beforBitmap.getWidth();
        float beforeHeight = beforBitmap.getHeight();
        if (beforeWidth <= maxWidth && beforeHeight <= maxHeight) {
            return beforBitmap;
        }

        // 计算宽高缩放率，等比例缩放
        float scaleWidth =  ((float) maxWidth) / beforeWidth;
        float scaleHeight = ((float)maxHeight) / beforeHeight;
        float scale = scaleWidth;
        if (scaleWidth > scaleHeight) {
            scale = scaleHeight;
        }
        Log.d("BitmapUtils", "before[" + beforeWidth + ", " + beforeHeight + "] max[" + maxWidth
                + ", " + maxHeight + "] scale:" + scale);

        // 矩阵对象
        Matrix matrix = new Matrix();
        // 缩放图片动作 缩放比例
        matrix.postScale(scale, scale);
        // 创建一个新的Bitmap 从原始图像剪切图像
        Bitmap afterBitmap = Bitmap.createBitmap(beforBitmap, 0, 0,
                (int) beforeWidth, (int) beforeHeight, matrix, true);
        return afterBitmap;
    }
}