使用 scaledBitmap 创建透明/镜像效果时避免致命内存错误答案

【问题标题】：Avoiding Fatal Memory Errors while creating a transparancy / mirror image effect using scaledBitmap使用 scaledBitmap 创建透明/镜像效果时避免致命内存错误
【发布时间】：2016-03-02 03:24:40
【问题描述】：

我正在尝试执行一些内存管理，看来我需要先缩放图像才能使用它 - 问题是 - 我不确定如何在保持我创建的镜像/透明效果。

应用程序在此行崩溃：

Bitmap bitmapWithReflection = Bitmap.createBitmap(width 
                      , (height + height/2), Config.ARGB_8888);

我已经尝试实现：

                Bitmap reflectionImage = Bitmap.createScaledBitmap(originalImage, height/2, height/2, false);

但是，这是不正确的，并导致另一个致命的崩溃，在我的 logcat 中没有任何价值：

              11-27 17:30:58.206: I/art(2111): Clamp target GC heap from 99MB to 96MB
11-27 17:31:01.354: I/Process(2111): Sending signal. PID: 2111 SIG: 9
11-27 17:31:42.609: I/Process(2235): Sending signal. PID: 2235 SIG: 9

如何避免这种情况？

Logcat：

11-27 17:26:00.490: D/AndroidRuntime(1953): Shutting down VM
11-27 17:26:00.492: E/AndroidRuntime(1953): FATAL EXCEPTION: main
11-27 17:26:00.492: E/AndroidRuntime(1953): Process: com.cb, PID: 1953
11-27 17:26:00.492: E/AndroidRuntime(1953): java.lang.OutOfMemoryError: Failed to allocate a 10898412 byte allocation with 1855424 free bytes and 1811KB until OOM
11-27 17:26:00.492: E/AndroidRuntime(1953):     at dalvik.system.VMRuntime.newNonMovableArray(Native Method)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.graphics.Bitmap.nativeCreate(Native Method)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.graphics.Bitmap.createBitmap(Bitmap.java:812)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.graphics.Bitmap.createBitmap(Bitmap.java:789)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.graphics.Bitmap.createBitmap(Bitmap.java:756)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at com.cb.CoverFlowExample$ImageAdapter.createReflectedImages(CoverFlowExample.java:133)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at com.cb.CoverFlowExample.onCreate(CoverFlowExample.java:47)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.Activity.performCreate(Activity.java:5990)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.ActivityThread.access$800(ActivityThread.java:151)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.os.Handler.dispatchMessage(Handler.java:102)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.os.Looper.loop(Looper.java:135)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at android.app.ActivityThread.main(ActivityThread.java:5254)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at java.lang.reflect.Method.invoke(Native Method)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at java.lang.reflect.Method.invoke(Method.java:372)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
11-27 17:26:00.492: E/AndroidRuntime(1953):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
11-27 17:26:04.564: I/Process(1953): Sending signal. PID: 1953 SIG: 9

来源：

 int index = 0;
                for (int imageId : mImageIds) {
                    Bitmap originalImage = BitmapFactory.decodeResource(getResources(), 
                            imageId);
                    int width = originalImage.getWidth();
                    int height = originalImage.getHeight();


                    //This will not scale but will flip on the Y axis
                    Matrix matrix = new Matrix();
                    matrix.preScale(1, -1);

                    //Create a Bitmap with the flip matrix applied to it.
                    //We only want the bottom half of the image
                    Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);


                    //Create a new bitmap with same width but taller to fit reflection
                    Bitmap bitmapWithReflection = Bitmap.createBitmap(width 
                      , (height + height/2), Config.ARGB_8888);

                   //Create a new Canvas with the bitmap that's big enough for
                   //the image plus gap plus reflection
                   Canvas canvas = new Canvas(bitmapWithReflection);
                   //Draw in the original image
                   canvas.drawBitmap(originalImage, 0, 0, null);
                   //Draw in the gap
                   Paint deafaultPaint = new Paint();
                   canvas.drawRect(0, height, width, height + reflectionGap, deafaultPaint);
                   //Draw in the reflection
                   canvas.drawBitmap(reflectionImage,0, height + reflectionGap, null);

                   //Create a shader that is a linear gradient that covers the reflection
                   Paint paint = new Paint(); 
                   LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, 
                     bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, 
                     TileMode.CLAMP); 
                   //Set the paint to use this shader (linear gradient)
                   paint.setShader(shader); 
                   //Set the Transfer mode to be porter duff and destination in
                   paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN)); 
                   //Draw a rectangle using the paint with our linear gradient
                   canvas.drawRect(0, height, width, 
                     bitmapWithReflection.getHeight() + reflectionGap, paint); 

                   ImageView imageView = new ImageView(mContext);
                   imageView.setImageBitmap(bitmapWithReflection);
                   imageView.setLayoutParams(new CoverFlow.LayoutParams(1900, 1500));
                   imageView.setScaleType(ScaleType.FIT_XY);
                   mImages[index++] = imageView;

                }
                return true;
        }

【问题讨论】：

先缩放，然后应用效果？ IE。在初始 decodeResource 步骤加载较少
我试过了，但它仍然崩溃：Bitmap originalImage = BitmapFactory.decodeResource(getResources(), imageId); int 宽度 = originalImage.getWidth(); int height = originalImage.getHeight(); Bitmap.createScaledBitmap(originalImage, height, width, false);
您能告诉我如何实现吗？我也试过这个：Bitmap preoriginalImage = BitmapFactory.decodeResource(getResources(), imageId); int width = preoriginalImage.getWidth(); int height = preoriginalImage.getHeight();位图 originalImage = Bitmap.createScaledBitmap(preoriginalImage, width, height, false);
stackoverflow.com/questions/16408505/… 有一个例子你可以告诉decodeResource 加载一个缩小的图像。 inSampleSize 因素也在 developer.android.com/training/displaying-bitmaps/… 中解释
感谢您的帮助-我感觉我越来越近了，但它仍然崩溃-您能看一下吗？ pastebin.com/SSMgE4Fj

标签： java android memory-management out-of-memory fatal-error

【解决方案1】：

缩放图像的最基本版本是指定样本大小。或者换句话说，告诉位图解码器只解码每个第 n 个像素和行。所以 2 意味着如果原始图像是 1000x1000，它只加载 500x500，这意味着内存减少了 4。

BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 2;
int index = 0;
for (int imageId : mImageIds) {
    Bitmap originalImage = BitmapFactory.decodeResource(getResources(),
            imageId, options);

这可能还不够，具体取决于尺寸、您使用的图片、手机和其他几个因素。这里有一篇文章

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

这解释了最重要的部分。

【讨论】：