Bitmap——BitmapFactory.Options

最新推荐文章于 2024-04-06 12:36:07 发布

转载最新推荐文章于 2024-04-06 12:36:07 发布 · 314 阅读

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本文介绍如何使用BitmapFactory.Options减少图片加载时的内存占用，并提供了一种根据屏幕尺寸调整图片大小的方法。

转自http://blog.youkuaiyun.com/ruiyiin/article/details/8675361

加载和显示图片是很消耗内存的一件事，BitmapFactory.Options 类, 允许我们定义图片以何种方式如何读到内存，

BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();  
bmpFactoryOptions.inSampleSize = 8;  
Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions);  
imv.setImageBitmap(bmp);

上面的代码使图片变成原来的1/8.

    //imv = (ImageView) findViewById(R.id.ReturnedImageView);  
            Display currentDisplay = getWindowManager().getDefaultDisplay();  
            int dw = currentDisplay.getWidth();  
            int dh = currentDisplay.getHeight();  
              try  
           {  
            BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();  
            bmpFactoryOptions.inJustDecodeBounds = true;  
            Bitmap bmp = BitmapFactory.decodeStream(getContentResolver().  
                    openInputStream(imageFileUri), null,  bmpFactoryOptions);  
      
            int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh);  
            int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw);  
      
            Log.v("HEIGHRATIO", ""+heightRatio);  
            Log.v("WIDTHRATIO", ""+widthRatio);  
      
            if (heightRatio > 1 && widthRatio > 1)  
            {  
                bmpFactoryOptions.inSampleSize =  heightRatio > widthRatio ? heightRatio:widthRatio;  
            }  
            bmpFactoryOptions.inJustDecodeBounds = false;  
            bmp = BitmapFactory.decodeStream(getContentResolver().  
                    openInputStream(imageFileUri), null,  bmpFactoryOptions);  
               returnedImageView.setImageBitmap(bmp);  
           }  
           catch (FileNotFoundException e)  
           {  
               Log.v("ERROR", e.toString());  
      
           }

上面的代码让图片根据窗口大小改变

bmpFactoryOptions.inJustDecodeBounds = true;

这一行让代码只解码图片的Bounds