使用JNI和NDK旋转位图

Question

背景:

我已经决定,由于位图会占用大量内存,而这些内存很容易导致内存不足错误,因此我会对C/C++代码进行大量内存消耗.

我用来旋转位图的步骤是:

1. 读取位图信息(宽度,高度)
2. 将位图像素存储到数组中.
3. 回收位图.
4. 创建一个相反大小的新位图.
5. 将像素放入新的位图.
6. 释放像素并返回位图.

问题:

即使一切似乎都没有任何错误,输出图像也不是原始的旋转.事实上,它完全毁了它.

旋转应该是逆时针方向,90度.

我获得的示例(屏幕截图放大):

所以你可以看到,不仅颜色变得怪异,而且尺寸与我设定的尺寸不符.这里真的很奇怪.

也许我没有正确读取/放置数据？

当然这只是一个例子.代码应该可以在任何位图上正常工作,只要设备有足够的内存来容纳它.另外,我可能想在位图上执行其他操作而不是旋转它.

我创建的代码:

Android.mk文件:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE    := JniTest
LOCAL_SRC_FILES := JniTest.cpp
LOCAL_LDLIBS := -llog
LOCAL_LDFLAGS += -ljnigraphics
include $(BUILD_SHARED_LIBRARY)
APP_OPTIM := debug
LOCAL_CFLAGS := -g

cpp文件:

#include <jni.h>
#include <jni.h>
#include <android/log.h>
#include <stdio.h>
#include <android/bitmap.h>
#include <cstring>
#include <unistd.h>

#define  LOG_TAG    "DEBUG"
#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

extern "C"
  {
  JNIEXPORT jobject JNICALL Java_com_example_jnitest_MainActivity_rotateBitmapCcw90(JNIEnv * env, jobject obj, jobject bitmap);
  }

JNIEXPORT jobject JNICALL Java_com_example_jnitest_MainActivity_rotateBitmapCcw90(JNIEnv * env, jobject obj, jobject bitmap)
  {
  //
  //getting bitmap info:
  //
  LOGD("reading bitmap info...");
  AndroidBitmapInfo info;
  int ret;
  if ((ret = AndroidBitmap_getInfo(env, bitmap, &info)) < 0)
    {
    LOGE("AndroidBitmap_getInfo() failed ! error=%d", ret);
    return NULL;
    }
  LOGD("width:%d height:%d stride:%d", info.width, info.height, info.stride);
  if (info.format != ANDROID_BITMAP_FORMAT_RGBA_8888)
    {
    LOGE("Bitmap format is not RGBA_8888!");
    return NULL;
    }
  //
  //read pixels of bitmap into native memory :
  //
  LOGD("reading bitmap pixels...");
  void* bitmapPixels;
  if ((ret = AndroidBitmap_lockPixels(env, bitmap, &bitmapPixels)) < 0)
    {
    LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
    return NULL;
    }
  uint32_t* src = (uint32_t*) bitmapPixels;
  uint32_t* tempPixels = new uint32_t[info.height * info.width];
  int stride = info.stride;
  int pixelsCount = info.height * info.width;
  memcpy(tempPixels, src, sizeof(uint32_t) * pixelsCount);
  AndroidBitmap_unlockPixels(env, bitmap);
  //
  //recycle bitmap - using bitmap.recycle()
  //
  LOGD("recycling bitmap...");
  jclass bitmapCls = env->GetObjectClass(bitmap);
  jmethodID recycleFunction = env->GetMethodID(bitmapCls, "recycle", "()V");
  if (recycleFunction == 0)
    {
    LOGE("error recycling!");
    return NULL;
    }
  env->CallVoidMethod(bitmap, recycleFunction);
  //
  //creating a new bitmap to put the pixels into it - using Bitmap Bitmap.createBitmap (int width, int height, Bitmap.Config config) :
  //
  LOGD("creating new bitmap...");
  jmethodID createBitmapFunction = env->GetStaticMethodID(bitmapCls, "createBitmap", "(IILandroid/graphics/Bitmap$Config;)Landroid/graphics/Bitmap;");
  jstring configName = env->NewStringUTF("ARGB_8888");
  jclass bitmapConfigClass = env->FindClass("android/graphics/Bitmap$Config");
  jmethodID valueOfBitmapConfigFunction = env->GetStaticMethodID(bitmapConfigClass, "valueOf", "(Ljava/lang/String;)Landroid/graphics/Bitmap$Config;");
  jobject bitmapConfig = env->CallStaticObjectMethod(bitmapConfigClass, valueOfBitmapConfigFunction, configName);
  jobject newBitmap = env->CallStaticObjectMethod(bitmapCls, createBitmapFunction, info.height, info.width, bitmapConfig);
  //
  // putting the pixels into the new bitmap:
  //
  if ((ret = AndroidBitmap_lockPixels(env, newBitmap, &bitmapPixels)) < 0)
    {
    LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
    return NULL;
    }
  uint32_t* newBitmapPixels = (uint32_t*) bitmapPixels;
  int whereToPut = 0;    
  for (int x = info.width - 1; x >= 0; --x)
    for (int y = 0; y < info.height; ++y)
      {
      uint32_t pixel = tempPixels[info.width * y + x];
      newBitmapPixels[whereToPut++] = pixel;
      }
  AndroidBitmap_unlockPixels(env, newBitmap);
  //
  // freeing the native memory used to store the pixels
  //
  delete[] tempPixels;
  return newBitmap;
  }

java文件:

  static
    {
    System.loadLibrary("JniTest");
    }

  /**
   * rotates a bitmap by 90 degrees counter-clockwise . <br/>
   * notes:<br/>
   * -the input bitmap will be recycled and shouldn't be used anymore <br/>
   * -returns the rotated bitmap . <br/>
   * -could take some time , so do the operation in a new thread
   */
  public native Bitmap rotateBitmapCcw90(Bitmap bitmap);

...
  Bitmap rotatedImage=rotateBitmapCcw90(bitmapToRotate);

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编辑:在得到我的答案之后,我希望与大家分享这些代码和说明:

• 为了使它工作,我在代码中用"uint32_t"替换了每个"uint16_t"的实例(这就是我所询问的代码中的错误).

• 输入和输出位图必须是8888配置(这是ARGB)

• 输入位图将在此过程中回收.

• 代码将图像逆时针旋转90度.当然,您可以根据需要进行更改.

---

更好的解决

我已经由具有此功能和其他人,一个不错的职位在这里.

Answer 1

由于你使用ARGB_8888格式,每个像素uint32_t都不是uint16_t.尝试更改旋转的位图创建以uint32_t用于源和目标阵列,它应该更好地工作.