【Android Demo】加载.gif格式图片
Android系统为了节省内存，一般不支持直接显示gif图片，即使你强制设置了，也只会显示图片的第一帧。
这个 Demo 是在网上看到的，是个思路，还是有些局限性，还是记录下，以后研究吧。
1.效果图：
2.实现原理：
通过解码gif图片形成多张静态图，然后通过线程和imageView来实现循环播放
3.准备GIF图片
4.详细代码
<1>工具类：CommonUtil.java
package com.yanis.tools; import java.io.InputStream; import com.yanis.tools.GifHelper.GifFrame; public class CommonUtil { /** * 解码GIF图片 * * @param is * @return */ public static GifFrame[] getGif(InputStream is) { GifHelper gifHelper = new GifHelper(); if (GifHelper.STATUS_OK == gifHelper.read(is)) { return gifHelper.getFrames(); } return null; } /** * 判断图片是否为GIF格式 * @param is * @return */ public static boolean isGif(InputStream is) { GifHelper gifHelper = new GifHelper(); return gifHelper.isGif(is); } }
<2>解码类：GifHelper.java
package com.yanis.tools; import java.io.InputStream; import java.util.Vector; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; //Handler for read & extract Bitmap from *.gif public class GifHelper { // to store *.gif data, Bitmap & delay public static class GifFrame { // to access image & delay w/o interface public Bitmap image; public int delay; public GifFrame(Bitmap im, int del) { image = im; delay = del; } } // to define some error type public static final int STATUS_OK = 0; public static final int STATUS_FORMAT_ERROR = 1; public static final int STATUS_OPEN_ERROR = 2; protected int status; protected InputStream in; protected int width; // full image width protected int height; // full image height protected boolean gctFlag; // global color table used protected int gctSize; // size of global color table protected int loopCount = 1; // iterations; 0 = repeat forever protected int[] gct; // global color table protected int[] lct; // local color table protected int[] act; // active color table protected int bgIndex; // background color index protected int bgColor; // background color protected int lastBgColor; // previous bg color protected int pixelAspect; // pixel aspect ratio protected boolean lctFlag; // local color table flag protected boolean interlace; // interlace flag protected int lctSize; // local color table size protected int ix, iy, iw, ih; // current image rectangle protected int lrx, lry, lrw, lrh; protected Bitmap image; // current frame protected Bitmap lastImage; // previous frame protected int frameindex = 0; public int getFrameindex() { return frameindex; } public void setFrameindex(int frameindex) { this.frameindex = frameindex; if (frameindex > frames.size() - 1) { frameindex = 0; } } protected byte[] block = new byte[256]; // current data block protected int blockSize = 0; // block size // last graphic control extension info protected int dispose = 0; // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev protected int lastDispose = 0; protected boolean transparency = false; // use transparent color protected int delay = 0; // delay in milliseconds protected int transIndex; // transparent color index protected static final int MaxStackSize = 4096; // max decoder pixel stack size // LZW decoder working arrays protected short[] prefix; protected byte[] suffix; protected byte[] pixelStack; protected byte[] pixels; protected Vector<GifFrame> frames; // frames read from current file protected int frameCount; // to get its Width / Height public int getWidth() { return width; } public int getHeigh() { return height; } /** * Gets display duration for specified frame. * * @param n * int index of frame * @return delay in milliseconds */ public int getDelay(int n) { delay = -1; if ((n >= 0) && (n < frameCount)) { delay = ((GifFrame) frames.elementAt(n)).delay; } return delay; } public int getFrameCount() { return frameCount; } public Bitmap getImage() { return getFrame(0); } public int getLoopCount() { return loopCount; } protected void setPixels() { int[] dest = new int[width * height]; // fill in starting image contents based on last image's dispose code if (lastDispose > 0) { if (lastDispose == 3) { // use image before last int n = frameCount - 2; if (n > 0) { lastImage = getFrame(n - 1); } else { lastImage = null; } } if (lastImage != null) { lastImage.getPixels(dest, 0, width, 0, 0, width, height); // copy pixels if (lastDispose == 2) { // fill last image rect area with background color int c = 0; if (!transparency) { c = lastBgColor; } for (int i = 0; i < lrh; i++) { int n1 = (lry + i) * width + lrx; int n2 = n1 + lrw; for (int k = n1; k < n2; k++) { dest[k] = c; } } } } } // copy each source line to the appropriate place in the destination int pass = 1; int inc = 8; int iline = 0; for (int i = 0; i < ih; i++) { int line = i; if (interlace) { if (iline >= ih) { pass++; switch (pass) { case 2: iline = 4; break; case 3: iline = 2; inc = 4; break; case 4: iline = 1; inc = 2; } } line = iline; iline += inc; } line += iy; if (line < height) { int k = line * width; int dx = k + ix; // start of line in dest int dlim = dx + iw; // end of dest line if ((k + width) < dlim) { dlim = k + width; // past dest edge } int sx = i * iw; // start of line in source while (dx < dlim) { // map color and insert in destination int index = ((int) pixels[sx++]) & 0xff; int c = act[index]; if (c != 0) { dest[dx] = c; } dx++; } } } image = Bitmap.createBitmap(dest, width, height, Config.RGB_565); } public Bitmap getFrame(int n) { Bitmap im = null; if ((n >= 0) && (n < frameCount)) { im = ((GifFrame) frames.elementAt(n)).image; } return im; } public GifFrame[] getFrames() { if(null != frames) return frames.toArray(new GifFrame[0]); return null; } public Bitmap nextBitmap() { frameindex++; if (frameindex > frames.size() - 1) { frameindex = 0; } return ((GifFrame) frames.elementAt(frameindex)).image; } public int nextDelay() { return ((GifFrame) frames.elementAt(frameindex)).delay; } // to read & parse all *.gif stream public int read(InputStream is) { init(); if (is != null) { in = is; readHeader(); if (!err()) { readContents(); if (frameCount < 0) { status = STATUS_FORMAT_ERROR; } } } else { status = STATUS_OPEN_ERROR; } try { is.close(); } catch (Exception e) { e.printStackTrace(); } return status; } public boolean isGif(InputStream is) { init(); if (is != null) { in = is; String id = ""; for (int i = 0; i < 6; i++) { id += (char) read(); } if (!id.toUpperCase().startsWith("GIF")) { return false; } } try { is.close(); } catch (Exception e) { e.printStackTrace(); } return true; } protected void decodeImageData() { int NullCode = -1; int npix = iw * ih; int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi; if ((pixels == null) || (pixels.length < npix)) { pixels = new byte[npix]; // allocate new pixel array } if (prefix == null) { prefix = new short[MaxStackSize]; } if (suffix == null) { suffix = new byte[MaxStackSize]; } if (pixelStack == null) { pixelStack = new byte[MaxStackSize + 1]; } // Initialize GIF data stream decoder. data_size = read(); clear = 1 << data_size; end_of_information = clear + 1; available = clear + 2; old_code = NullCode; code_size = data_size + 1; code_mask = (1 << code_size) - 1; for (code = 0; code < clear; code++) { prefix[code] = 0; suffix[code] = (byte) code; } // Decode GIF pixel stream. datum = bits = count = first = top = pi = bi = 0; for (i = 0; i < npix;) { if (top == 0) { if (bits < code_size) { // Load bytes until there are enough bits for a code. if (count == 0) { // Read a new data block. count = readBlock(); if (count <= 0) { break; } bi = 0; } datum += (((int) block[bi]) & 0xff) << bits; bits += 8; bi++; count--; continue; } // Get the next code. code = datum & code_mask; datum >>= code_size; bits -= code_size; // Interpret the code if ((code > available) || (code == end_of_information)) { break; } if (code == clear) { // Reset decoder. code_size = data_size + 1; code_mask = (1 << code_size) - 1; available = clear + 2; old_code = NullCode; continue; } if (old_code == NullCode) { pixelStack[top++] = suffix[code]; old_code = code; first = code; continue; } in_code = code; if (code == available) { pixelStack[top++] = (byte) first; code = old_code; } while (code > clear) { pixelStack[top++] = suffix[code]; code = prefix[code]; } first = ((int) suffix[code]) & 0xff; // Add a new string to the string table, if (available >= MaxStackSize) { break; } pixelStack[top++] = (byte) first; prefix[available] = (short) old_code; suffix[available] = (byte) first; available++; if (((available & code_mask) == 0) && (available < MaxStackSize)) { code_size++; code_mask += available; } old_code = in_code; } // Pop a pixel off the pixel stack. top--; pixels[pi++] = pixelStack[top]; i++; } for (i = pi; i < npix; i++) { pixels[i] = 0; // clear missing pixels } } protected boolean err() { return status != STATUS_OK; } // to initia variable protected void init() { status = STATUS_OK; frameCount = 0; frames = new Vector<GifFrame>(); gct = null; lct = null; } protected int read() { int curByte = 0; try { curByte = in.read(); } catch (Exception e) { status = STATUS_FORMAT_ERROR; } return curByte; } protected int readBlock() { blockSize = read(); int n = 0; if (blockSize > 0) { try { int count = 0; while (n < blockSize) { count = in.read(block, n, blockSize - n); if (count == -1) { break; } n += count; } } catch (Exception e) { e.printStackTrace(); } if (n < blockSize) { status = STATUS_FORMAT_ERROR; } } return n; } // Global Color Table protected int[] readColorTable(int ncolors) { int nbytes = 3 * ncolors; int[] tab = null; byte[] c = new byte[nbytes]; int n = 0; try { n = in.read(c); } catch (Exception e) { e.printStackTrace(); } if (n < nbytes) { status = STATUS_FORMAT_ERROR; } else { tab = new int[256]; // max size to avoid bounds checks int i = 0; int j = 0; while (i < ncolors) { int r = ((int) c[j++]) & 0xff; int g = ((int) c[j++]) & 0xff; int b = ((int) c[j++]) & 0xff; tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b; } } return tab; } // Image Descriptor protected void readContents() { // read GIF file content blocks boolean done = false; while (!(done || err())) { int code = read(); switch (code) { case 0x2C: // image separator readImage(); break; case 0x21: // extension code = read(); switch (code) { case 0xf9: // graphics control extension readGraphicControlExt(); break; case 0xff: // application extension readBlock(); String app = ""; for (int i = 0; i < 11; i++) { app += (char) block[i]; } if (app.equals("NETSCAPE2.0")) { readNetscapeExt(); } else { skip(); // don't care } break; default: // uninteresting extension skip(); } break; case 0x3b: // terminator done = true; break; case 0x00: // bad byte, but keep going and see what happens break; default: status = STATUS_FORMAT_ERROR; } } } protected void readGraphicControlExt() { read(); // block size int packed = read(); // packed fields dispose = (packed & 0x1c) >> 2; // disposal method if (dispose == 0) { dispose = 1; // elect to keep old image if discretionary } transparency = (packed & 1) != 0; delay = readShort() * 10; // delay in milliseconds transIndex = read(); // transparent color index read(); // block terminator } // to get Stream - Head protected void readHeader() { String id = ""; for (int i = 0; i < 6; i++) { id += (char) read(); } if (!id.toUpperCase().startsWith("GIF")) { status = STATUS_FORMAT_ERROR; return; } readLSD(); if (gctFlag && !err()) { gct = readColorTable(gctSize); bgColor = gct[bgIndex]; } } protected void readImage() { // offset of X ix = readShort(); // (sub)image position & size // offset of Y iy = readShort(); // width of bitmap iw = readShort(); // height of bitmap ih = readShort(); // Local Color Table Flag int packed = read(); lctFlag = (packed & 0x80) != 0; // 1 - local color table flag // Interlace Flag, to array with interwoven if ENABLE, with order // otherwise interlace = (packed & 0x40) != 0; // 2 - interlace flag // 3 - sort flag // 4-5 - reserved lctSize = 2 << (packed & 7); // 6-8 - local color table size if (lctFlag) { lct = readColorTable(lctSize); // read table act = lct; // make local table active } else { act = gct; // make global table active if (bgIndex == transIndex) { bgColor = 0; } } int save = 0; if (transparency) { save = act[transIndex]; act[transIndex] = 0; // set transparent color if specified } if (act == null) { status = STATUS_FORMAT_ERROR; // no color table defined } if (err()) { return; } decodeImageData(); // decode pixel data skip(); if (err()) { return; } frameCount++; // create new image to receive frame data image = Bitmap.createBitmap(width, height, Config.RGB_565); // createImage(width, height); setPixels(); // transfer pixel data to image frames.addElement(new GifFrame(image, delay)); // add image to frame // list if (transparency) { act[transIndex] = save; } resetFrame(); } // Logical Screen Descriptor protected void readLSD() { // logical screen size width = readShort(); height = readShort(); // packed fields int packed = read(); gctFlag = (packed & 0x80) != 0; // 1 : global color table flag // 2-4 : color resolution // 5 : gct sort flag gctSize = 2 << (packed & 7); // 6-8 : gct size bgIndex = read(); // background color index pixelAspect = read(); // pixel aspect ratio } protected void readNetscapeExt() { do { readBlock(); if (block[0] == 1) { // loop count sub-block int b1 = ((int) block[1]) & 0xff; int b2 = ((int) block[2]) & 0xff; loopCount = (b2 << 8) | b1; } } while ((blockSize > 0) && !err()); } // read 8 bit data protected int readShort() { // read 16-bit value, LSB first return read() | (read() << 8); } protected void resetFrame() { lastDispose = dispose; lrx = ix; lry = iy; lrw = iw; lrh = ih; lastImage = image; lastBgColor = bgColor; dispose = 0; transparency = false; delay = 0; lct = null; } /** * Skips variable length blocks up to and including next zero length block. */ protected void skip() { do { readBlock(); } while ((blockSize > 0) && !err()); } }
<3>Activity显示:MainActivity.java
package com.yanis.gifphoto; import java.io.FileInputStream; import java.io.InputStream; import android.app.Activity; import android.graphics.Bitmap; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; import android.view.ViewGroup.LayoutParams; import android.widget.ImageView; import android.widget.ImageView.ScaleType; import com.yanis.tools.CommonUtil; import com.yanis.tools.GifHelper.GifFrame; public class MainActivity extends Activity { private PlayGifTask mGifTask; ImageView iv; GifFrame[] frames; FileInputStream fis=null; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); iv = new ImageView(this); iv.setScaleType(ScaleType.CENTER); setContentView(iv, new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); //对Gif图片进行解码 final InputStream fis = getResources().openRawResource(R.drawable.gidpic); /*try { fis = new FileInputStream(new File(Environment.getExternalStorageDirectory()+File.separator+"/tmp/111.gif")); } catch (FileNotFoundException e) { e.printStackTrace(); }*/ frames = CommonUtil.getGif(fis); mGifTask = new PlayGifTask(iv, frames); mGifTask.startTask(); Thread th=new Thread(mGifTask); th.start(); } @Override protected void onDestroy() { super.onDestroy(); if(null != mGifTask) mGifTask.stopTask(); } //用来循环播放Gif每帧图片 private class PlayGifTask implements Runnable { int i = 0; ImageView iv; GifFrame[] frames; int framelen,oncePlayTime=0; public PlayGifTask(ImageView iv, GifFrame[] frames) { this.iv = iv; this.frames = frames; int n=0; framelen=frames.length; while(n<framelen){ oncePlayTime+=frames[n].delay; n++; } Log.d("msg", "playTime= "+oncePlayTime); //Gif图片单次播放时长 } Handler h2=new Handler(){ public void handleMessage(Message msg) { switch(msg.what){ case 1: iv.setImageBitmap((Bitmap)msg.obj); break; } }; }; @Override public void run() { if (!frames[i].image.isRecycled()) { // iv.setImageBitmap(frames[i].image); Message m=Message.obtain(h2, 1, frames[i].image); m.sendToTarget(); } iv.postDelayed(this, frames[i++].delay); i %= framelen; } public void startTask() { iv.post(this); } public void stopTask() { if(null != iv) iv.removeCallbacks(this); iv = null; if(null != frames) { for(GifFrame frame : frames) { if(frame.image != null && !frame.image.isRecycled()) { frame.image.recycle(); frame.image = null; } } frames = null; // mGifTask=null; } } } }
