Animated GIF support on Android.

MovieView.java

package com.mypackage;

import java.util.ArrayList;
import java.util.Date;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;

//Shows bitmaps on timer. Can be a part of an Android layout.

public class MovieView extends View
{
    long m_ts;
    Handler m_h = new Handler();
    Runnable m_Inval = new Runnable()
    {
        public void run()
        {
            invalidate();
        }
    };
    
    static class Frame
    {
        private Bitmap bm;
        private int l, t;
        private int Delay;
        @SuppressWarnings("unused")
        private int Disp;
    }
    
    private ArrayList<Frame> m_Frames = null;
    private int m_Pos;
    private Paint m_Paint = new Paint();
    private Canvas m_Canvas;
    private Bitmap m_Surface;
    private Rect m_SrcRc, m_DestRc;

    public MovieView(Context Ctxt)
    {
        super(Ctxt);
    }
    
    public MovieView(Context Ctxt, AttributeSet a)
    {
        super(Ctxt, a);
    }		
    
    @Override
    public void draw(Canvas c)
    {
        super.draw(c);
        if(m_Frames != null)
        {
            Frame f = m_Frames.get(m_Pos);
            m_Canvas.drawBitmap(f.bm, f.l, f.t, m_Paint);
            c.drawBitmap(m_Surface, m_SrcRc, m_DestRc, m_Paint);
            m_Pos = (m_Pos + 1) % m_Frames.size();
            if(f.Delay > 0)
            {
                m_h.removeCallbacks(m_Inval);
                m_h.postDelayed(m_Inval, f.Delay);
            }
            else
                invalidate();
        }
    }
    
    public void Reset(int n)
    {
        m_Frames = new ArrayList<Frame>(n);
    }

    public void AddFrame(Bitmap bm, int l, int t, int Delay, int Disp)
    {
        Frame f = new Frame();
        f.bm = bm;
        f.Delay = Delay;
        f.Disp = Disp;
        f.l = l;
        f.t = t;
        m_Frames.add(f);
    }
    
    //Assumes that the frames have been built
    public void Start()
    {
        m_Pos = 0;
        Bitmap bm = m_Frames.get(0).bm; //First frame
        m_Surface = bm.copy(bm.getConfig(), true);
        m_Canvas = new Canvas(m_Surface);
        int bw, bh;
        m_SrcRc = new Rect(0, 0, (bw = m_Surface.getWidth())-1, (bh = m_Surface.getHeight())-1);
        int w = getWidth(), h = getHeight();
        //Letterboxing logic conditional on large size???
        if(w*bh > bw*h) //Needs letterboxing on width
        {
            int dx = (w - (h*bw)/bh)/2;
            m_DestRc = new Rect(dx, 0, w-2*dx - 1, h-1);
        }
        else
        {
            int dy = (h - (w*bh)/bw)/2;
            m_DestRc = new Rect(0, dy, w-1, h-2*dy - 1);
        }
            
        m_ts = new Date().getTime();
        invalidate();
    }
    
    public void Stop()
    {
        m_Frames = null;
        m_Surface = null;
        m_Canvas = null;
        m_h.removeCallbacks(m_Inval);
        invalidate();
    }
}

MyClass.cpp

#include <jni.h>
#include "gif_lib.h"

//Native counterpart to the MyClass class
//Requires giflib sources and headers! They're in the archive that's attached to the comment below.

extern "C"
{
    //Replace "com_mypackage_MyClass" with your own package/class
    jboolean JNIEXPORT Java_com_mypackage_MyClass_LoadGIF(JNIEnv *jni, jobject self, jstring jfile, jboolean bHighColor)
    {
        const char *File = jni->GetStringUTFChars(jfile, 0);
        GifFileType *g = DGifOpenFileName(File);
        jni->ReleaseStringUTFChars(jfile, File);
        if (!g)
            return JNI_FALSE;
        if (DGifSlurp(g) != GIF_OK)
        {
            DGifCloseFile(g);
            return JNI_FALSE;
        }

        jclass cl = jni->GetObjectClass(self);

        jni->CallVoidMethod(self, jni->GetMethodID(cl, "StartImage", "(I)V"), (jint)g->ImageCount);

        jmethodID afmid = jni->GetMethodID(cl, "AddFrame", "(IIIIII[B)V");
        if (!afmid)
        {
            DGifCloseFile(g);
            return JNI_FALSE;
        }

        int i, Frame;
        unsigned int Colors[256];
        //TODO: don't rebuild colors if there's a global color table only
        for (Frame = 0; Frame<g->ImageCount; Frame++)
        {
            SavedImage &si = g->SavedImages[Frame];
            int Delay = 0;
            int TransColor = -1;
            jint Disp = 0;
            for (i = 0; i<si.ExtensionBlockCount; i++)
            {
                ExtensionBlock &eb = si.ExtensionBlocks[i];
                if (eb.Function == 0xf9) //Animation!
                {
                    char c = eb.Bytes[0];
                    Delay = (int)(unsigned char)(eb.Bytes[1]) | ((int)(unsigned char)(eb.Bytes[2]) << 8);
                    if (c & 1)
                        TransColor = (unsigned char)(eb.Bytes[3]);
                    Disp = (c >> 2) & 7;
                }
            }

            //Now format the bits...
            GifImageDesc &id = si.ImageDesc;
            ColorMapObject *cm = id.ColorMap ? id.ColorMap : g->SColorMap;
            int w = id.Width, h = id.Height;
            int wh = w*h;
            int Size = wh * (bHighColor ? 4 : 2); //Size in bytes - in RGBA-4444 format, 2 bytes per pixel, in RGBA-8888, 4
            unsigned char *Buf = (unsigned char*)malloc(Size);
            if (!Buf)
            {
                DGifCloseFile(g);
                return JNI_FALSE;
            }
            //Translate the color map into RGBA-4444 or RGBA-8888 format, take alpha into account. 256 colors tops, static is OK
            for (i = 0; i<cm->ColorCount; i++)
            {
                GifColorType &c = cm->Colors[i];
                Colors[i] =
                    bHighColor ?
                    ((unsigned int)c.Red << 16) |
                    ((unsigned int)c.Green << 8) |
                    ((unsigned int)c.Blue) |
                    0xff000000
                    :
                    ((unsigned short)(c.Red & 0xf0) << 8) |
                    ((unsigned short)(c.Green & 0xf0) << 4) |
                    c.Blue | 0xf;
            }
            if (TransColor != -1)
                Colors[TransColor] = 0;

            //Convert pixel by pixel...
            unsigned char *pSrc = si.RasterBits;
            if (bHighColor)
            {
                unsigned int *pDest = (unsigned int*)Buf;
                for (i = 0; i<wh; i++)
                    *pDest++ = Colors[*pSrc++];
            }
            else
            {
                unsigned short *pDest = (unsigned short*)Buf;
                for (i = 0; i<wh; i++)
                    *pDest++ = (unsigned short)(Colors[*pSrc++]);
            }

            jbyteArray ja = jni->NewByteArray(Size);
            if (!ja)
            {
                free(Buf);
                DGifCloseFile(g);
                return JNI_FALSE;
            }
            jni->SetByteArrayRegion(ja, 0, Size, (jbyte*)Buf);
            free(Buf);

            jni->CallVoidMethod(self, afmid,
                (jint)Delay * 10,
                (jint)id.Left, (jint)id.Top,
                (jint)w, (jint)h, Disp, ja);
            jni->DeleteLocalRef(ja);
        }
        DGifCloseFile(g);
        return JNI_TRUE;
    }
}

MyClass.java

package com.mypackage;

//This is a sample. In a real project, there'd be a Dialog or an Activity that hosts the MovieView.

class MyClass 
{ 
    private MovieView m_mv; //initialized on loading
    private static s_bHighColor = true;
    //Format; hard-coded here
    
    //This native method's implementation in in MyClass.cpp
    private native boolean LoadGIF(String FileName, boolean bHighColor); 

    //loadLibrary() is called elsewhere 
    //Called from JNI - do not mess with it. 
    private void AddFrame(int Delay, int l, int t, int w, int h, int  Disp, byte [] Bits) 
    { 
        Bitmap bm = Bitmap.createBitmap(w, h,
        s_bHighColor ?
            Bitmap.Config.ARGB_8888 :
            Bitmap.Config.ARGB_4444); 
        bm.copyPixelsFromBuffer(ByteBuffer.wrap(Bits)); 
        m_mv.AddFrame(bm, l, t, Delay, Disp); 
    } 
    //Called from JNI - do not mess with it. 
    private void StartImage(int FrameCount) 
    { 
        m_mv.Reset(FrameCount); 
    } 
//////////////////////////////// The animation starts here
    public void StartMovie(File f) 
    { 
        if(LoadGIF(f.getAbsolutePath(), s_bHighColor))
        //This will call Reset(), AddFrames() 
            m_mv.Start(); 
    }
}

The attached file contains the required giflib sources and headers. It's a zip archive, renamed to keep the Gist comment system happy.

Explanations for the whole thing are here.