一个好用的android图片压缩工具类

╰+哭是因爲堅強的太久メ 2022-08-06 07:27 146阅读 0赞

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">用了很久图片压缩，之前人们一直使用google的官方图片压缩方法</span>

final BitmapFactory.Options options = new BitmapFactory.Options();
    		options.inJustDecodeBounds = true;
    		BitmapFactory.decodeResource(res, resId, options);
    		
    		options.inSampleSize = calculateInSampleSize(options, reqWidth,
    				reqHeight);
    		options.inJustDecodeBounds = false;
    		return BitmapFactory.decodeResource(res, resId, options);

public static int calculateInSampleSize(
                BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;
    
        if (height > reqHeight || width > reqWidth) {
    
            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
    
            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) > reqHeight
                    && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }
    
        return inSampleSize;
    }

代码来自google

http://developer.android.com/training/displaying-bitmaps/load-bitmap.html

仔细看calucelateInSamplesize方法，该算法返回的是一种压缩比例，仔细一看他的计算过程，你会发现，inSampleSize的变化过程是2-4-8,，而真正进入wile循环时，宽高就已经被看成是小了一半来计算的了，所以，上面那个网站说12M能压缩到0.75M,就是因为差距太大，如果安卓手机内部压缩自己的图片(大概是2M压缩到100K)，所以此时，这个方法就适用于android编码压缩了。

所以鄙人针对于android编码时压缩，在此对它进行了优化，优化后代码如下：

运行:   culculateInSampleSize(bm,200,300)效果:

\* 计算压缩比例值(改进版 by touch\_ping)  
\*   
\* 原版2>4>8...倍压缩  
\* 当前2>3>4...倍压缩  
\*   
\* @param options  
\*            解析图片的配置信息  
\* @param reqWidth  
\*            所需图片压缩尺寸最小宽度  
\* @param reqHeight  
\*            所需图片压缩尺寸最小高度  
\* @return  
\*/  
public static int calculateInSampleSize(BitmapFactory.Options options,  
int reqWidth, int reqHeight) \{  
  
final int picheight = options.outHeight;  
final int picwidth = options.outWidth;  
Log.i("test", "原尺寸:" +  picwidth + "\*" +picheight);  
  
int targetheight = picheight;  
int targetwidth = picwidth;  
int inSampleSize = 1;  
  
if (targetheight > reqHeight || targetwidth > reqWidth) \{  
while (targetheight  >= reqHeight  
&& targetwidth>= reqWidth) \{  
Log.i("test","压缩:" +inSampleSize + "倍");  
inSampleSize += 1;  
targetheight = picheight/inSampleSize;  
targetwidth = picwidth/inSampleSize;  
\}  
\}  
  
Log.i("test","最终压缩比例:" +inSampleSize + "倍");  
Log.i("test", "新尺寸:" +  targetwidth + "\*" +targetheight);  
return inSampleSize;  
\}

压缩效果如下：

![Image 1][]

文件大小从1.12M变成81.75k

最终附上完整压缩工具类:

package com.example.mqtest;
    
    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    
    import android.content.res.Resources;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.util.Log;
    
    /**
     * 图片压缩工具类
     * @author touch_ping
     * 2015-1-5 下午1:29:59
     */
    public class BitmapCompressor {
    	/**
    	 * 质量压缩
    	 * @author ping 2015-1-5 下午1:29:58
    	 * @param image
    	 * @param maxkb
    	 * @return
    	 */
    	public static Bitmap compressBitmap(Bitmap image,int maxkb) {
    		//L.showlog("压缩图片");
    		ByteArrayOutputStream baos = new ByteArrayOutputStream();
    		image.compress(Bitmap.CompressFormat.JPEG, 50, baos);// 质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中
    		int options = 100;
    //		Log.i("test","原始大小" + baos.toByteArray().length);
    		while (baos.toByteArray().length / 1024 > maxkb) { // 循环判断如果压缩后图片是否大于(maxkb)50kb,大于继续压缩
    //			Log.i("test","压缩一次!");
    			baos.reset();// 重置baos即清空baos
    			options -= 10;// 每次都减少10
    			image.compress(Bitmap.CompressFormat.JPEG, options, baos);// 这里压缩options%，把压缩后的数据存放到baos中
    		}
    //		Log.i("test","压缩后大小" + baos.toByteArray().length);
    		ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把压缩后的数据baos存放到ByteArrayInputStream中
    		Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream数据生成图片
    		return bitmap;
    	}
    	
    	/**
    	 * http://developer.android.com/training/displaying-bitmaps/load-bitmap.html
    	 * 官网：获取压缩后的图片
    	 * 
    	 * @param res
    	 * @param resId
    	 * @param reqWidth
    	 *            所需图片压缩尺寸最小宽度
    	 * @param reqHeight
    	 *            所需图片压缩尺寸最小高度
    	 * @return
    	 */
    	public static Bitmap decodeSampledBitmapFromResource(Resources res,
    			int resId, int reqWidth, int reqHeight) {
    		final BitmapFactory.Options options = new BitmapFactory.Options();
    		options.inJustDecodeBounds = true;
    		BitmapFactory.decodeResource(res, resId, options);
    		
    		options.inSampleSize = calculateInSampleSize(options, reqWidth,
    				reqHeight);
    		options.inJustDecodeBounds = false;
    		return BitmapFactory.decodeResource(res, resId, options);
    	}
    
    	/**
    	 * 官网：获取压缩后的图片
    	 * 
    	 * @param res
    	 * @param resId
    	 * @param reqWidth
    	 *            所需图片压缩尺寸最小宽度
    	 * @param reqHeight
    	 *            所需图片压缩尺寸最小高度
    	 * @return
    	 */
    	public static Bitmap decodeSampledBitmapFromFile(String filepath,
    			int reqWidth, int reqHeight) {
    		final BitmapFactory.Options options = new BitmapFactory.Options();
    		options.inJustDecodeBounds = true;
    		BitmapFactory.decodeFile(filepath, options);
    
    		options.inSampleSize = calculateInSampleSize(options, reqWidth,
    				reqHeight);
    		options.inJustDecodeBounds = false;
    		return BitmapFactory.decodeFile(filepath, options);
    	}
    
    	public static Bitmap decodeSampledBitmapFromBitmap(Bitmap bitmap,
    			int reqWidth, int reqHeight) {
    		ByteArrayOutputStream baos = new ByteArrayOutputStream();
    		bitmap.compress(Bitmap.CompressFormat.PNG, 90, baos);
    		byte[] data = baos.toByteArray();
    		
    		final BitmapFactory.Options options = new BitmapFactory.Options();
    		options.inJustDecodeBounds = true;
    		BitmapFactory.decodeByteArray(data, 0, data.length, options);
    		options.inSampleSize = calculateInSampleSize(options, reqWidth,
    				reqHeight);
    		options.inJustDecodeBounds = false;
    		return BitmapFactory.decodeByteArray(data, 0, data.length, options);
    	}
    
    	/**
    	 * 计算压缩比例值(改进版 by touch_ping)
    	 * 
    	 * 原版2>4>8...倍压缩
    	 * 当前2>3>4...倍压缩
    	 * 
    	 * @param options
    	 *            解析图片的配置信息
    	 * @param reqWidth
    	 *            所需图片压缩尺寸最小宽度O
    	 * @param reqHeight
    	 *            所需图片压缩尺寸最小高度
    	 * @return
    	 */
    	public static int calculateInSampleSize(BitmapFactory.Options options,
    			int reqWidth, int reqHeight) {
    		
    		final int picheight = options.outHeight;
    		final int picwidth = options.outWidth;
    		Log.i("test", "原尺寸:" +  picwidth + "*" +picheight);
    		
    		int targetheight = picheight;
    		int targetwidth = picwidth;
    		int inSampleSize = 1;
    		
    		if (targetheight > reqHeight || targetwidth > reqWidth) {
    			while (targetheight  >= reqHeight
    					&& targetwidth>= reqWidth) {
    				Log.i("test","压缩:" +inSampleSize + "倍");
    				inSampleSize += 1;
    				targetheight = picheight/inSampleSize;
    				targetwidth = picwidth/inSampleSize;
    			}
    		}
    		
    		Log.i("test","最终压缩比例:" +inSampleSize + "倍");
    		Log.i("test", "新尺寸:" +  targetwidth + "*" +targetheight);
    		return inSampleSize;
    	}
    }

[Image 1]: