Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
An optimized implementation of GifDecoder for Android devices.
Implementation of GifDecoder that is more memory efficient to animate for Android devices.
This implementation does not house in memory a Bitmap for every image frame. Images are instead decoded
on-the-fly, and only the minimum data to create the next frame in the sequence is kept. The
implementation has also been adapted to reduce memory allocations in the decoding process to reduce
time to render each frame.
Adapted from: http://show.docjava.com/book/cgij/exportToHTML/ip/gif/stills/GifDecoder.java.html
/**
* Copyright (c) 2013 Xcellent Creations, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package com.example.decoder;
import android.graphics.Bitmap;
import android.util.Log;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.ArrayList;
/**
* Reads frame data from a GIF image source and decodes it into individual frames
* for animation purposes. Image data can be read from either and InputStream source
* or a byte[].
*
* This class is optimized for running animations with the frames, there
* are no methods to get individual frame images, only to decode the next frame in the
* animation sequence. Instead, it lowers its memory footprint by only housing the minimum
* data necessary to decode the next frame in the animation sequence.
*
* The animation must be manually moved forward using {@link #advance()} before requesting the next
* frame. This method must also be called before you request the first frame or an error will
* occur.
*
* Implementation adapted from sample code published in Lyons. (2004). <em>Java for Programmers</em>,
* republished under the MIT Open Source License
*/
public class GifDecoder {
private static final String TAG = GifDecoder.class.getSimpleName();
/**
* File read status: No errors.
*/
public static final int STATUS_OK = 0;
/**
* File read status: Error decoding file (may be partially decoded)
*/
public static final int STATUS_FORMAT_ERROR = 1;
/**
* File read status: Unable to open source.
*/
public static final int STATUS_OPEN_ERROR = 2;
/**
* max decoder pixel stack size
*/
protected static final int MAX_STACK_SIZE = 4096;
/**
* GIF Disposal Method meaning take no action
*/
private static final int DISPOSAL_UNSPECIFIED = 0;
/**
* GIF Disposal Method meaning leave canvas from previous frame
*/
private static final int DISPOSAL_NONE = 1;
/**
* GIF Disposal Method meaning clear canvas to background color
*/
private static final int DISPOSAL_BACKGROUND = 2;
/**
* GIF Disposal Method meaning clear canvas to frame before last
*/
private static final int DISPOSAL_PREVIOUS = 3;
/**
* Global status code of GIF data parsing
*/
protected int status;
//Global File Header values and parsing flags
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[] act; // active color table
protected int bgIndex; // background color index
protected int bgColor; // background color
protected int pixelAspect; // pixel aspect ratio
protected boolean lctFlag; // local color table flag
protected int lctSize; // local color table size
// Raw GIF data from input source
protected ByteBuffer rawData;
// Raw data read working array
protected byte[] block = new byte[256]; // current data block
protected int blockSize = 0; // block size last graphic control extension info
// LZW decoder working arrays
protected short[] prefix;
protected byte[] suffix;
protected byte[] pixelStack;
protected byte[] mainPixels;
protected int[] mainScratch, copyScratch;
protected ArrayList<GifFrame> frames; // frames read from current file
protected GifFrame currentFrame;
protected Bitmap previousImage, currentImage, renderImage;
protected int framePointer;
protected int frameCount;
/**
* Inner model class housing metadata for each frame
*/
private static class GifFrame {
public int ix, iy, iw, ih;
/* Control Flags */
public boolean interlace;
public boolean transparency;
/* Disposal Method */
public int dispose;
/* Transparency Index */
public int transIndex;
/* Delay, in ms, to next frame */
public int delay;
/* Index in the raw buffer where we need to start reading to decode */
public int bufferFrameStart;
/* Local Color Table */
public int[] lct;
}
/**
* Move the animation frame counter forward
*/
public void advance() {
framePointer = (framePointer + 1) % frameCount;
}
/**
* Gets display duration for specified frame.
*
* @param n int index of frame
* @return delay in milliseconds
*/
public int getDelay(int n) {
int delay = -1;
if ((n >= 0) && (n < frameCount)) {
delay = frames.get(n).delay;
}
return delay;
}
/**
* Gets display duration for the upcoming frame
*/
public int getNextDelay() {
if (frameCount <=0 || framePointer < 0) {
return -1;
}
return getDelay(framePointer);
}
/**
* Gets the number of frames read from file.
*
* @return frame count
*/
public int getFrameCount() {
return frameCount;
}
/**
* Gets the current index of the animation frame, or -1 if animation hasn't not yet started
*
* @return frame index
*/
public int getCurrentFrameIndex() {
return framePointer;
}
/**
* Gets the "Netscape" iteration count, if any. A count of 0 means repeat indefinitiely.
*
* @return iteration count if one was specified, else 1.
*/
public int getLoopCount() {
return loopCount;
}
/**
* Get the next frame in the animation sequence.
*
* @return Bitmap representation of frame
*/
public Bitmap getNextFrame() {
if (frameCount <= 0 || framePointer < 0 || currentImage == null) {
return null;
}
GifFrame frame = frames.get(framePointer);
//Set the appropriate color table
if (frame.lct == null) {
act = gct;
} else {
act = frame.lct;
if (bgIndex == frame.transIndex) {
bgColor = 0;
}
}
int save = 0;
if (frame.transparency) {
save = act[frame.transIndex];
act[frame.transIndex] = 0; // set transparent color if specified
}
if (act == null) {
Log.w(TAG, "No Valid Color Table");
status = STATUS_FORMAT_ERROR; // no color table defined
return null;
}
setPixels(framePointer); // transfer pixel data to image
// Reset the transparent pixel in the color table
if (frame.transparency) {
act[frame.transIndex] = save;
}
return currentImage;
}
/**
* Reads GIF image from stream
*
* @param is containing GIF file.
* @return read status code (0 = no errors)
*/
public int read(InputStream is, int contentLength) {
long startTime = System.currentTimeMillis();
if (is != null) {
try {
int capacity = (contentLength > 0) ? (contentLength + 4096) : 4096;
ByteArrayOutputStream buffer = new ByteArrayOutputStream(capacity);
int nRead;
byte[] data = new byte[16384];
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush();
read(buffer.toByteArray());
} catch (IOException e) {
Log.w(TAG, "Error reading data from stream", e);
}
} else {
status = STATUS_OPEN_ERROR;
}
try {
is.close();
} catch (Exception e) {
Log.w(TAG, "Error closing stream", e);
}
return status;
}
/**
* Reads GIF image from byte array
*
* @param data containing GIF file.
* @return read status code (0 = no errors)
*/
public int read(byte[] data) {
init();
if (data != null) {
//Initiliaze the raw data buffer
rawData = ByteBuffer.wrap(data);
rawData.rewind();
rawData.order(ByteOrder.LITTLE_ENDIAN);
readHeader();
if (!err()) {
readContents();
if (frameCount < 0) {
status = STATUS_FORMAT_ERROR;
}
}
} else {
status = STATUS_OPEN_ERROR;
}
return status;
}
/**
* Creates new frame image from current data (and previous frames as specified by their disposition codes).
*/
protected void setPixels(int frameIndex) {
GifFrame currentFrame = frames.get(frameIndex);
GifFrame previousFrame = null;
int previousIndex = frameIndex - 1;
if (previousIndex >= 0) {
previousFrame = frames.get(previousIndex);
}
// final location of blended pixels
final int[] dest = mainScratch;
// fill in starting image contents based on last image's dispose code
if (previousFrame != null && previousFrame.dispose > DISPOSAL_UNSPECIFIED) {
if (previousFrame.dispose == DISPOSAL_NONE && currentImage != null) {
// Start with the current image
currentImage.getPixels(dest, 0, width, 0, 0, width, height);
}
if (previousFrame.dispose == DISPOSAL_BACKGROUND) {
// Start with a canvas filled with the background color
int c = 0;
if (!currentFrame.transparency) {
c = bgColor;
}
for (int i = 0; i < previousFrame.ih; i++) {
int n1 = (previousFrame.iy + i) * width + previousFrame.ix;
int n2 = n1 + previousFrame.iw;
for (int k = n1; k < n2; k++) {
dest[k] = c;
}
}
}
if (previousFrame.dispose == DISPOSAL_PREVIOUS && previousImage != null) {
// Start with the previous frame
previousImage.getPixels(dest, 0, width, 0, 0, width, height);
}
}
//Decode pixels for this frame into the global pixels[] scratch
decodeBitmapData(currentFrame, mainPixels); // decode pixel data
// 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 < currentFrame.ih; i++) {
int line = i;
if (currentFrame.interlace) {
if (iline >= currentFrame.ih) {
pass++;
switch (pass) {
case 2:
iline = 4;
break;
case 3:
iline = 2;
inc = 4;
break;
case 4:
iline = 1;
inc = 2;
break;
default:
break;
}
}
line = iline;
iline += inc;
}
line += currentFrame.iy;
if (line < height) {
int k = line * width;
int dx = k + currentFrame.ix; // start of line in dest
int dlim = dx + currentFrame.iw; // end of dest line
if ((k + width) < dlim) {
dlim = k + width; // past dest edge
}
int sx = i * currentFrame.iw; // start of line in source
while (dx < dlim) {
// map color and insert in destination
int index = ((int) mainPixels[sx++]) & 0xff;
int c = act[index];
if (c != 0) {
dest[dx] = c;
}
dx++;
}
}
}
//Copy pixels into previous image
currentImage.getPixels(copyScratch, 0, width, 0, 0, width, height);
previousImage.setPixels(copyScratch, 0, width, 0, 0, width, height);
//Set pixels for current image
currentImage.setPixels(dest, 0, width, 0, 0, width, height);
}
/**
* Decodes LZW image data into pixel array. Adapted from John Cristy's BitmapMagick.
*/
protected void decodeBitmapData(GifFrame frame, byte[] dstPixels) {
long startTime = System.currentTimeMillis();
long stepOne, stepTwo, stepThree;
if (frame != null) {
//Jump to the frame start position
rawData.position(frame.bufferFrameStart);
}
int nullCode = -1;
int npix = (frame == null) ? width * height : frame.iw * frame.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 (dstPixels == null || dstPixels.length < npix) {
dstPixels = new byte[npix]; // allocate new pixel array
}
if (prefix == null) {
prefix = new short[MAX_STACK_SIZE];
}
if (suffix == null) {
suffix = new byte[MAX_STACK_SIZE];
}
if (pixelStack == null) {
pixelStack = new byte[MAX_STACK_SIZE + 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; // XXX ArrayIndexOutOfBoundsException
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 >= MAX_STACK_SIZE) {
break;
}
pixelStack[top++] = (byte) first;
prefix[available] = (short) old_code;
suffix[available] = (byte) first;
available++;
if (((available & code_mask) == 0) && (available < MAX_STACK_SIZE)) {
code_size++;
code_mask += available;
}
old_code = in_code;
}
// Pop a pixel off the pixel stack.
top--;
dstPixels[pi++] = pixelStack[top];
i++;
}
for (i = pi; i < npix; i++) {
dstPixels[i] = 0; // clear missing pixels
}
}
/**
* Returns true if an error was encountered during reading/decoding
*/
protected boolean err() {
return status != STATUS_OK;
}
/**
* Initializes or re-initializes reader
*/
protected void init() {
status = STATUS_OK;
frameCount = 0;
framePointer = -1;
frames = new ArrayList<GifFrame>();
gct = null;
}
/**
* Reads a single byte from the input stream.
*/
protected int read() {
int curByte = 0;
try {
curByte = (rawData.get() & 0xFF);
} catch (Exception e) {
status = STATUS_FORMAT_ERROR;
}
return curByte;
}
/**
* Reads next variable length block from input.
*
* @return number of bytes stored in "buffer"
*/
protected int readBlock() {
blockSize = read();
int n = 0;
if (blockSize > 0) {
try {
int count;
while (n < blockSize) {
count = blockSize - n;
rawData.get(block, n, count);
n += count;
}
} catch (Exception e) {
Log.w(TAG, "Error Reading Block", e);
status = STATUS_FORMAT_ERROR;
}
}
return n;
}
/**
* Reads color table as 256 RGB integer values
*
* @param ncolors int number of colors to read
* @return int array containing 256 colors (packed ARGB with full alpha)
*/
protected int[] readColorTable(int ncolors) {
int nbytes = 3 * ncolors;
int[] tab = null;
byte[] c = new byte[nbytes];
try {
rawData.get(c);
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;
}
} catch (BufferUnderflowException e) {
Log.w(TAG, "Format Error Reading Color Table", e);
status = STATUS_FORMAT_ERROR;
}
return tab;
}
/**
* Main file parser. Reads GIF content blocks.
*/
protected void readContents() {
// read GIF file content blocks
boolean done = false;
while (!(done || err())) {
int code = read();
switch (code) {
case 0x2C: // image separator
readBitmap();
break;
case 0x21: // extension
code = read();
switch (code) {
case 0xf9: // graphics control extension
//Start a new frame
currentFrame = new GifFrame();
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;
case 0xfe:// comment extension
skip();
break;
case 0x01:// plain text extension
skip();
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;
}
}
}
/**
* Reads GIF file header information.
*/
protected void readHeader() {
String id = "";
for (int i = 0; i < 6; i++) {
id += (char) read();
}
if (!id.startsWith("GIF")) {
status = STATUS_FORMAT_ERROR;
return;
}
readLSD();
if (gctFlag && !err()) {
gct = readColorTable(gctSize);
bgColor = gct[bgIndex];
}
}
/**
* Reads Graphics Control Extension values
*/
protected void readGraphicControlExt() {
read(); // block size
int packed = read(); // packed fields
currentFrame.dispose = (packed & 0x1c) >> 2; // disposal method
if (currentFrame.dispose == 0) {
currentFrame.dispose = 1; // elect to keep old image if discretionary
}
currentFrame.transparency = (packed & 1) != 0;
currentFrame.delay = readShort() * 10; // delay in milliseconds
currentFrame.transIndex = read(); // transparent color index
read(); // block terminator
}
/**
* Reads next frame image
*/
protected void readBitmap() {
currentFrame.ix = readShort(); // (sub)image position & size
currentFrame.iy = readShort();
currentFrame.iw = readShort();
currentFrame.ih = readShort();
int packed = read();
lctFlag = (packed & 0x80) != 0; // 1 - local color table flag interlace
lctSize = (int) Math.pow(2, (packed & 0x07) + 1);
// 3 - sort flag
// 4-5 - reserved lctSize = 2 << (packed & 7); // 6-8 - local color
// table size
currentFrame.interlace = (packed & 0x40) != 0;
if (lctFlag) {
currentFrame.lct = readColorTable(lctSize); // read table
} else {
currentFrame.lct = null; //No local color table
}
currentFrame.bufferFrameStart = rawData.position(); //Save this as the decoding position pointer
decodeBitmapData(null, mainPixels); // false decode pixel data to advance buffer
skip();
if (err()) {
return;
}
frameCount++;
frames.add(currentFrame); // add image to frame
}
/**
* Reads 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
//Now that we know the size, init scratch arrays
mainPixels = new byte[width * height];
mainScratch = new int[width * height];
copyScratch = new int[width * height];
previousImage = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
currentImage = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
}
/**
* Reads Netscape extenstion to obtain iteration count
*/
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());
}
/**
* Reads next 16-bit value, LSB first
*/
protected int readShort() {
// read 16-bit value
return rawData.getShort();
}
/**
* Skips variable length blocks up to and including next zero length block.
*/
protected void skip() {
do {
readBlock();
} while ((blockSize > 0) && !err());
}
}

Do you have any idea on what causes/how to fix the ArrayIndexOutOfBoundsException on line 449?

I am now using this code to decode gif. Most of images can be decoded well, but for some ones (like format GIF89a, you can find such images on http://9gag.com), this doesn't work well. Please help to check. Thanks!

I want to show animated gifs in a ListView downloaded from a web. So, I use GifDecoder to build AnimationDrawable from all the frames for every image in a list, but images are static.
Here is the code:

final AnimationDrawable animationDrawable = new AnimationDrawable();
final GifDecoder gifDecoder = new GifDecoder();
gifDecoder.read(data); //data is a byte array
final int frameCount = gifDecoder.getFrameCount();
for (int i = 0; i < frameCount; i++) {
gifDecoder.advance();
bitmap = gifDecoder.getNextFrame();
int delay = gifDecoder.getDelay(i);
android.util.Log.v("Decode", "===>Frame " + i + ": " + delay + "]");
animationDrawable.addFrame(new BitmapDrawable(bitmap), delay);
}
Could you please help me to clarify what the problem is?

Thanks

grennis commented Feb 23, 2014

It uses 30% CPU on my Nexus 4 to play an animated gif with fairly fast frame sequences. It shouldn't be hard to port to C and call with JNI?

cxp1991 commented Jun 26, 2014

But CPU usage increases.
My app displays many gif at the same time.
How do I reduce CPU usage?
Thanks!

Did anyone have a problem where this gifDecoder interprets black color (0x000000) as transparent?

o-antsiferov ->
Replace
bitmap = gifDecoder.getNextFrame();
with
bitmap = Bitmap.createBitmap(gifDecoder.getNextFrame());
and AnimationDrawable should work fine.

If you want the gif to display with transparent background, change these lines

previousImage = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
currentImage = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);

to

previousImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
currentImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

Does anyone know how do we get the previous frame in the gif with the help of this gif decoder ? You can only get the next frame in the gif list. Is there a way you can access the previous frame or an i-th frame of the gif ?

If anyone stumbles across this, I would just like to point out that this version doesn't implement deferred clear codes (in LZW), so GIFs that implement that part of the spec will appear broken.

@smdmustaffa the frames can build upon each other, so you can't go backwards, you have to start from 0th to get ith, but you can generate all like https://gist.github.com/devunwired/4479231#gistcomment-990915 did and then random-access to your heart's content.

Hello!

I am using this code for a Gif manipulation but encountered a problem. If I read an image it is not complete. It looks like the drawing stopped near the end of the process. The Gif file is 485x240px and I tried to raise the MAX_STACK_SIZE but it didn't help.

Thankful for any inspiration!

ads001 commented Nov 18, 2017

@Sacredgamer I am facing the same problem, try this
https://github.com/shaopx/InCompleteGifDecoder
it helps me .

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment