原文:
Android截屏淺析
鏈接:http://blog.sina.com.cn/s/blog_69a04cf4010173fz.html
Android的調試工具DDMS提供截屏功能,很多同步軟件例如豌豆莢也都提供截屏功能,經分析Android截屏原理大致如下:
DDMS是通過adb調用設備端的adbd(ADBdaemon)提供的framebufferservice進行截屏(源碼在system/core/adb/framebuffer_service.c),在較早版本的Android中,framebuffer service通過直接讀framebuffer 設備(/dev/graphics/fb0)來截屏,在較新版本的Android中,framebuffer service則調用截屏工具screencap來截屏。那些同步軟件也是調用screencap實現截屏的。
screencap是Android原生自帶的工具,是一個C寫的可執行文件,在設備上的/system/bin/下面可以找到它,screencap截屏後可保存爲PNG格式文件或RGBRAW文件。
screencap的源碼在frameworks/base/cmds/screencap/,它調用SurfaceFlinger提供的截屏接口ScreenshotClient,其源碼在frameworks/native/libs/gui/SurfaceComposerClient.cpp(該路徑在不同版本的Android源碼中可能略有差別),ScreenshotClient通過進程間通信調用SurfaceFlinger service的截屏功能,源碼在frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp中的函數SurfaceFlinger::captureScreen。
在各種截屏方法中,讀framebuffer設備(/dev/graphics/fb0)的方式在某些使用硬件overlay顯示的設備上可能無法截取到某些畫面(例如video playback和camera preview畫面),但是SurfaceFlinger提供的上述截屏接口則可以完美截取任何屏幕畫面,因此相對來說是Android上最正規最完善的截屏方法,使用起來也非常簡單。但需注意,ScreenshotClient等接口在不同Android版本上可能存在差異,例如在JellyBean的最新版本上ScreenshotClient的成員函數update增加了一個參數display(應該是爲了支持多個顯示設備),導致與之前版本不兼容。
此外Android還自帶另一個截屏工具screenshot,源碼在frameworks/base/cmds/screenshot/,它通過直接讀framebuffer 設備(/dev/graphics/fb0)來截屏,保存爲PNG格式文件。screenshot貌似沒有用處。
原文二:(用自己的方式實現截屏)
Android代碼截屏
鏈接:http://myhpu2008.iteye.com/blog/999779
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Rect;
import android.util.Log;
import android.view.View;
public class ScreenShot {
// 獲取指定Activity的截屏,保存到png文件
private static Bitmap takeScreenShot(Activity activity) {
// View是你需要截圖的View
View view = activity.getWindow().getDecorView();
view.setDrawingCacheEnabled(true);
view.buildDrawingCache();
Bitmap b1 = view.getDrawingCache();
// 獲取狀態欄高度
Rect frame = new Rect();
activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
int statusBarHeight = frame.top;
Log.i("TAG", "" + statusBarHeight);
// 獲取屏幕長和高
int width = activity.getWindowManager().getDefaultDisplay().getWidth();
int height = activity.getWindowManager().getDefaultDisplay()
.getHeight();
// 去掉標題欄
// Bitmap b = Bitmap.createBitmap(b1, 0, 25, 320, 455);
Bitmap b = Bitmap.createBitmap(b1, 0, statusBarHeight, width, height
- statusBarHeight);
view.destroyDrawingCache();
return b;
}
// 保存到sdcard
private static void savePic(Bitmap b, String strFileName) {
FileOutputStream fos = null;
try {
fos = new FileOutputStream(strFileName);
if (null != fos) {
b.compress(Bitmap.CompressFormat.PNG, 90, fos);
fos.flush();
fos.close();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
// 程序入口
public static void shoot(Activity a) {
ScreenShot.savePic(ScreenShot.takeScreenShot(a), "sdcard/xx.png");
}
}
需要注意的是,shoot方法只能在view已經被加載後方可調用。
或者在 @Override
public void onWindowFocusChanged(boolean hasFocus) {
// TODO Auto-generated method stub
super.onWindowFocusChanged(hasFocus);
ScreenShot.shoot(this);
}中調用
原文三:
淺談android截屏問題
鏈接:http://my.oschina.net/JumpLong/blog/75556
做了幾個月的截屏開發,稍微瞭解了一下這方面的知識,於是拿來分享一下,也許對你有一些幫助吧。
我是基於android2.3.3系統之上的,想必大家應該知道在android源碼下面有個文件叫做screencap吧,位於frameworks\base\services\surfaceflinger\tests\screencap\screencap.cpp,你直接在linux下編譯(就是去screencap的文件mm,然後保存在 /system/bin/test-screencap),然後push到手機上再通過電腦去敲命令./test-screencap /mnt/sdcard/scapxx.png就可以實現截屏(不要導入到/mntsdcard,反正我是導入到system目錄裏面纔可以執行)。
- /*
- * Copyright (C) 2010 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #include <utils/Log.h>
- #include <binder/IPCThreadState.h>
- #include <binder/ProcessState.h>
- #include <binder/IServiceManager.h>
- #include <binder/IMemory.h>
- #include <surfaceflinger/ISurfaceComposer.h>
- #include <SkImageEncoder.h>
- #include <SkBitmap.h>
- using namespace android;
- int main(int argc, char** argv)
- {
- if (argc != 2) {
- printf("usage: %s path\n", argv[0]);
- exit(0);
- }
- const String16 name("SurfaceFlinger");
- sp<ISurfaceComposer> composer;
- getService(name, &composer);
- sp<IMemoryHeap> heap;
- uint32_t w, h;
- PixelFormat f;
- status_t err = composer->captureScreen(0, &heap, &w, &h, &f, 0, 0);
- if (err != NO_ERROR) {
- fprintf(stderr, "screen capture failed: %s\n", strerror(-err));
- exit(0);
- }
- printf("screen capture success: w=%u, h=%u, pixels=%p\n",
- w, h, heap->getBase());
- printf("saving file as PNG in %s ...\n", argv[1]);
- SkBitmap b;
- b.setConfig(SkBitmap::kARGB_8888_Config, w, h);
- b.setPixels(heap->getBase());
- SkImageEncoder::EncodeFile(argv[1], b,
- SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality);
- return 0;
- }
其實這個程序真正用到的就是一個叫做capturescreen的函數,而capturescreen會調用captureScreenImplLocked這個函數
下面是代碼:
- status_t SurfaceFlinger::captureScreenImplLocked(DisplayID dpy,
- sp<IMemoryHeap>* heap,
- uint32_t* w, uint32_t* h, PixelFormat* f,
- uint32_t sw, uint32_t sh)
- {
- LOGI("captureScreenImplLocked");
- status_t result = PERMISSION_DENIED;
- // only one display supported for now
- if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
- return BAD_VALUE;
- if (!GLExtensions::getInstance().haveFramebufferObject())
- return INVALID_OPERATION;
- // get screen geometry
- const DisplayHardware& hw(graphicPlane(dpy).displayHardware());
- const uint32_t hw_w = hw.getWidth();
- const uint32_t hw_h = hw.getHeight();
- if ((sw > hw_w) || (sh > hw_h))
- return BAD_VALUE;
- sw = (!sw) ? hw_w : sw;
- sh = (!sh) ? hw_h : sh;
- const size_t size = sw * sh * 4;
- // make sure to clear all GL error flags
- while ( glGetError() != GL_NO_ERROR ) ;
- // create a FBO
- GLuint name, tname;
- glGenRenderbuffersOES(1, &tname);
- glBindRenderbufferOES(GL_RENDERBUFFER_OES, tname);
- glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_RGBA8_OES, sw, sh);
- glGenFramebuffersOES(1, &name);
- glBindFramebufferOES(GL_FRAMEBUFFER_OES, name);
- glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES,
- GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, tname);
- GLenum status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);
- if (status == GL_FRAMEBUFFER_COMPLETE_OES) {
- // invert everything, b/c glReadPixel() below will invert the FB
- glViewport(0, 0, sw, sh);
- glScissor(0, 0, sw, sh);
- glMatrixMode(GL_PROJECTION);
- glPushMatrix();
- glLoadIdentity();
- glOrthof(0, hw_w, 0, hw_h, 0, 1);
- glMatrixMode(GL_MODELVIEW);
- // redraw the screen entirely...
- glClearColor(0,0,0,1);
- glClear(GL_COLOR_BUFFER_BIT);
- const Vector< sp<LayerBase> >& layers(mVisibleLayersSortedByZ);
- const size_t count = layers.size();
- for (size_t i=0 ; i<count ; ++i) {
- const sp<LayerBase>& layer(layers[i]);
- layer->drawForSreenShot();
- }
- // XXX: this is needed on tegra
- glScissor(0, 0, sw, sh);
- // check for errors and return screen capture
- if (glGetError() != GL_NO_ERROR) {
- // error while rendering
- result = INVALID_OPERATION;
- } else {
- // allocate shared memory large enough to hold the
- // screen capture
- sp<MemoryHeapBase> base(
- new MemoryHeapBase(size, 0, "screen-capture") );
- void* const ptr = base->getBase();
- if (ptr) {
- // capture the screen with glReadPixels()
- glReadPixels(0, 0, sw, sh, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
- if (glGetError() == GL_NO_ERROR) {
- *heap = base;
- *w = sw;
- *h = sh;
- *f = PIXEL_FORMAT_RGBA_8888;
- result = NO_ERROR;
- }
- } else {
- result = NO_MEMORY;
- }
- }
- glEnable(GL_SCISSOR_TEST);
- glViewport(0, 0, hw_w, hw_h);
- glMatrixMode(GL_PROJECTION);
- glPopMatrix();
- glMatrixMode(GL_MODELVIEW);
- } else {
- result = BAD_VALUE;
- }
- // release FBO resources
- glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
- glDeleteRenderbuffersOES(1, &tname);
- glDeleteFramebuffersOES(1, &name);
- hw.compositionComplete();
- return result;
- }
- status_t SurfaceFlinger::captureScreen(DisplayID dpy,
- sp<IMemoryHeap>* heap,
- uint32_t* width, uint32_t* height, PixelFormat* format,
- uint32_t sw, uint32_t sh)
- {
- LOGI("into captureScreen");
- // only one display supported for now
- if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
- return BAD_VALUE;
- if (!GLExtensions::getInstance().haveFramebufferObject())
- return INVALID_OPERATION;
- class MessageCaptureScreen : public MessageBase {
- SurfaceFlinger* flinger;
- DisplayID dpy;
- sp<IMemoryHeap>* heap;
- uint32_t* w;
- uint32_t* h;
- PixelFormat* f;
- uint32_t sw;
- uint32_t sh;
- status_t result;
- public:
- MessageCaptureScreen(SurfaceFlinger* flinger, DisplayID dpy,
- sp<IMemoryHeap>* heap, uint32_t* w, uint32_t* h, PixelFormat* f,
- uint32_t sw, uint32_t sh)
- : flinger(flinger), dpy(dpy),
- heap(heap), w(w), h(h), f(f), sw(sw), sh(sh), result(PERMISSION_DENIED)
- {
- }
- status_t getResult() const {
- LOGI("getResult()");
- return result;
- }
- virtual bool handler() {
- LOGI("handler()");
- Mutex::Autolock _l(flinger->mStateLock);
- // if we have secure windows, never allow the screen capture
- if (flinger->mSecureFrameBuffer)
- return true;
- result = flinger->captureScreenImplLocked(dpy,
- heap, w, h, f, sw, sh);
- return true;
- }
- };
- LOGI("before messagecapturescreen");
- sp<MessageBase> msg = new MessageCaptureScreen(this,
- dpy, heap, width, height, format, sw, sh);
- status_t res = postMessageSync(msg);
- if (res == NO_ERROR) {
- res = static_cast<MessageCaptureScreen*>( msg.get() )->getResult();
- }
- return res;
- }
而這個函數關鍵又使用了opengl的幾個函數去獲得圖片,然而opengl又去read framebuffer(這是我的理解)。如果你去用jni調用so的方法去截屏的話,就可以把screencap這個文件稍微修改一下然後做成so文件,方法可以參考這篇博客:http://blog.csdn.net/zx19899891/article/details/7072291
主要是補充一下怎麼去存放文件與編譯吧,當然我說的方法只是我做的方法不代表是很好用的。
存放:在eclipse新建一個android工程,保存後找到這個工程(如screencap)的存放位置 然後把這個文件放到android源代碼的development文件裏面,然後在你的那個工程文件裏面新建一個文件夾,名字叫做jni(這個文件夾平行於src文件夾,screencap/jni),把上面博客提到的那個C++跟mk(screencap/jni/com_android_ScreenCap_ScreenCapNative.cpp和screencap/jni/Android.mk)文件放進去,最後在把編譯的mk文件放在screencap目錄下(screencap/Android.mk);
編譯:編譯是個很偉大的工程,需要你花大量的時間與精力。直接在終端進入工程存放的所在位置,我的是Administrator/Android.2.3.3/development,然後mm(Builds all of the modules in the current directory),如果成功,那麼你運氣比較好,在終端回提示你APK保存的位置。push進手機試一試。但是往往是不成功的。你可能會遇到一些問題,比如android.permission.ACCESS_SURFACE_FLINGER ,android.permission.READ_FRAME_BUFFER(因爲capturescrren這個函數是surfaceflinger裏面的函數,然而surfaceflinger裏面的opengl截屏函數會去讀取framebuffer),相關源代碼是:
- status_t SurfaceFlinger::onTransact(
- uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
- {
- switch (code) {
- case CREATE_CONNECTION:
- case OPEN_GLOBAL_TRANSACTION:
- case CLOSE_GLOBAL_TRANSACTION:
- case SET_ORIENTATION:
- case FREEZE_DISPLAY:
- case UNFREEZE_DISPLAY:
- case BOOT_FINISHED:
- case TURN_ELECTRON_BEAM_OFF:
- case TURN_ELECTRON_BEAM_ON:
- {
- // codes that require permission check
- IPCThreadState* ipc = IPCThreadState::self();
- const int pid = ipc->getCallingPid();
- const int uid = ipc->getCallingUid();
- if ((uid != AID_GRAPHICS) && !mAccessSurfaceFlinger.check(pid, uid)) {
- LOGE("Permission Denial: "
- "can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
- return PERMISSION_DENIED;
- }
- break;
- }
- case CAPTURE_SCREEN:
- {
- // codes that require permission check
- IPCThreadState* ipc = IPCThreadState::self();
- const int pid = ipc->getCallingPid();
- const int uid = ipc->getCallingUid();
- if ((uid != AID_GRAPHICS) && !mReadFramebuffer.check(pid, uid)) {
- LOGE("Permission Denial: "
- "can't read framebuffer pid=%d, uid=%d", pid, uid);
- return PERMISSION_DENIED;
- }
- break;
- }
- }
- status_t err = BnSurfaceComposer::onTransact(code, data, reply, flags);
- if (err == UNKNOWN_TRANSACTION || err == PERMISSION_DENIED) {
- CHECK_INTERFACE(ISurfaceComposer, data, reply);
- if (UNLIKELY(!mHardwareTest.checkCalling())) {
- IPCThreadState* ipc = IPCThreadState::self();
- const int pid = ipc->getCallingPid();
- const int uid = ipc->getCallingUid();
- LOGI("err");
- LOGE("Permission Denial: "
- "can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
- return PERMISSION_DENIED;
- }
- int n;
- switch (code) {
- case 1000: // SHOW_CPU, NOT SUPPORTED ANYMORE
- case 1001: // SHOW_FPS, NOT SUPPORTED ANYMORE
- return NO_ERROR;
- case 1002: // SHOW_UPDATES
- n = data.readInt32();
- mDebugRegion = n ? n : (mDebugRegion ? 0 : 1);
- return NO_ERROR;
- case 1003: // SHOW_BACKGROUND
- n = data.readInt32();
- mDebugBackground = n ? 1 : 0;
- return NO_ERROR;
- case 1004:{ // repaint everything
- Mutex::Autolock _l(mStateLock);
- const DisplayHardware& hw(graphicPlane(0).displayHardware());
- mDirtyRegion.set(hw.bounds()); // careful that's not thread-safe
- signalEvent();
- return NO_ERROR;
- }
- case 1005:{ // force transaction
- setTransactionFlags(eTransactionNeeded|eTraversalNeeded);
- return NO_ERROR;
- }
- case 1006:{ // enable/disable GraphicLog
- int enabled = data.readInt32();
- GraphicLog::getInstance().setEnabled(enabled);
- return NO_ERROR;
- }
- case 1007: // set mFreezeCount
- mFreezeCount = data.readInt32();
- mFreezeDisplayTime = 0;
- return NO_ERROR;
- case 1010: // interrogate.
- reply->writeInt32(0);
- reply->writeInt32(0);
- reply->writeInt32(mDebugRegion);
- reply->writeInt32(mDebugBackground);
- return NO_ERROR;
- case 1013: {
- Mutex::Autolock _l(mStateLock);
- const DisplayHardware& hw(graphicPlane(0).displayHardware());
- reply->writeInt32(hw.getPageFlipCount());
- }
- return NO_ERROR;
- }
- }
- return err;
- }
這個僅僅只是開始! 你會發現你即使在xml裏面添加相應的權限仍然會有這個問題出現,爲什麼呢?在packageManger文件裏面發現相關代碼:
- int checkSignaturesLP(Signature[] s1, Signature[] s2) {
- if (s1 == null) {
- return s2 == null
- ? PackageManager.SIGNATURE_NEITHER_SIGNED
- : PackageManager.SIGNATURE_FIRST_NOT_SIGNED;
- }
- if (s2 == null) {
- return PackageManager.SIGNATURE_SECOND_NOT_SIGNED;
- }
- HashSet<Signature> set1 = new HashSet<Signature>();
- for (Signature sig : s1) {
- set1.add(sig);
- }
- HashSet<Signature> set2 = new HashSet<Signature>();
- for (Signature sig : s2) {
- set2.add(sig);
- }
- // Make sure s2 contains all signatures in s1.
- if (set1.equals(set2)) {
- return PackageManager.SIGNATURE_MATCH;
- }
- return PackageManager.SIGNATURE_NO_MATCH;
- }
- Check for shared user signatures
- if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
- if (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
- pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
- Slog.e(TAG, "Package " + pkg.packageName
- + " has no signatures that match those in shared user "
- + pkgSetting.sharedUser.name + "; ignoring!");
- mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
- return false;
- }
- }
- return true;
- private boolean verifySignaturesLP(PackageSetting pkgSetting,
- PackageParser.Package pkg) {
- // Check for shared user signatures
- if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
- (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
- pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
- log.e(TAG, "Package " + pkg.packageName
- + " has no signatures that match those in shared user "
- + pkgSetting.sharedUser.name + "; ignoring!");
- mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
- return false;
- }
- }
- return true;
- }
你在終端輸入adb logcat | grep PackageManager 你會發現這兩個權限根本沒有賦予給你的apk,我的理解是,程序需要權限,然後apk仍然需要權限。那怎麼樣給apk賦予權限呢,兩個方法,一個是在我上面說的screencap/Android.mk裏面添加platform一行,然後在回到mm。還有一個方法就是通過sign。這兩個方法都是給apk賦予system權限,但是我試過這兩種方法,都有問題,就是在adb install的時候會顯示簽名不兼容,查看源代碼會發現uid跟gid不匹配。這些是我這段時間發現的問題,大家有問題可以交流交流。
再說說幾個簡單的應用層截屏吧,很簡單,就是幾個函數調用而已
- View view = getWindow().getDecorView();
- Display display = this.getWindowManager().getDefaultDisplay();
- view.layout(0, 0, display.getWidth(), display.getHeight());
- view.setDrawingCacheEnabled(true);//允許當前窗口保存緩存信息,這樣 getDrawingCache()方法纔會返回一個Bitmap
- Bitmap bmp = Bitmap.createBitmap(view.getDrawingCache());
我對這個程序的理解就是,它僅僅只能截取當前的activity,也就是說如果你運行這個程序後它就截取你這個程序的當前屏幕的信息。我們假設你做成一個按鈕,在點擊按鈕後sleep5秒再調用這個方法(假設你的activity叫做screen)。當你點擊按鈕以後,然後你再點擊home或者返回按鈕,等到5秒後你那個程序就會截取到你當前屏幕?不是!它只會截取那個運行於後臺的screen這個activity。
還有個截屏的方法就是用OPENGL。
這裏有我的opengl截屏的程序,方便的話可以下載後去看看。
http://www.oschina.net/code/snippet_729469_19233