Android Bitmap的优化

男娘i 2023-07-04 06:10 51阅读 0赞

#### 1、为什么需要对Bitmap进行优化 ####

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#### 2、优化方案 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 1]  
（1）、对图片资源的释放  
在 Android2.3.3（API 10）前，调用 Bitmap.recycle()方法

在 Android2.3.3（API 10）后，采用软引用（SoftReference）  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 2]  
（2）、根据分辨率适配 & 缩放图片  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 3]  
例如：

public class BitmapUtil {
    
        public static Bitmap ratio(String filePath, int pixelW, int pixelH) {
            BitmapFactory.Options newOptions = new BitmapFactory.Options();
            newOptions.inJustDecodeBounds = true;
            //位深度，如果图片不是特别大而肉眼又看不出来的话可设置低一点的位深度
            //默认8888是最高的位深度（图片质量最好的，每一位像素都要占用8个字节）
            newOptions.inPreferredConfig = Bitmap.Config.RGB_565;
            //预加载
            BitmapFactory.decodeFile(filePath, newOptions);
            //预加载以后我们就可以获取到图片的宽和高
            int originalW = newOptions.outWidth;
            int originalH = newOptions.outHeight;
            //取出宽高后就可以对它进行采样
            newOptions.inSampleSize = getSimpleSize(originalW, originalH, pixelW, pixelH);
            //这里要将它设为false（不再去只加载它的宽高）
            newOptions.inJustDecodeBounds = false;
            //获取了采样值以后就可以真正的对它进行加载
            return BitmapFactory.decodeFile(filePath, newOptions);
        }
    
        /**
         * 原始的宽高 要显示的宽高
         */
        private static int getSimpleSize(int originalW, int originalH, int pixelW, int pixelH) {
            int simpleSize = 1;//默认采样为1（不压缩）
            if (originalW > originalH && originalW > pixelW) {
                simpleSize = originalW / pixelW;//以宽度进行采样计算
            } else if (originalW < originalH && originalH > pixelH) {
                simpleSize = originalH / pixelH;//以高度进行采样计算
            }
            if (simpleSize <= 0) {
                simpleSize = 1;
            }
            return simpleSize;
        }
    
    }

（3）、按需 选择合适的解码方式  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 4]  
（4）、设置 图片缓存  
重复加载图片资源耗费太多资源（CPU、内存 & 流量）  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70 5]

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