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An integration library allowing users to re-encode or create animated GIFs
package com.bumptech.glide.gifencoder;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.Log;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* Class AnimatedGifEncoder - Encodes a GIF file consisting of one or more
* frames.
*
*
* Example:
* AnimatedGifEncoder e = new AnimatedGifEncoder();
* e.start(outputFileName);
* e.setDelay(1000); // 1 frame per sec
* e.addFrame(image1);
* e.addFrame(image2);
* e.addFrame(image3, 100, 100); // set position of the frame
* e.finish();
*
*
* No copyright asserted on the source code of this class. May be used for any
* purpose, however, refer to the Unisys LZW patent for restrictions on use of
* the associated LZWEncoder class. Please forward any corrections to
* [email protected].
*
* @author Kevin Weiner, FM Software
* @version 1.03 November 2003
*
*/
public class AnimatedGifEncoder {
private static final String TAG = "AnimatedGifEncoder";
// The minimum % of an images pixels that must be transparent for us to set a transparent index
// automatically.
private static final double MIN_TRANSPARENT_PERCENTAGE = 4d;
private int width; // image size
private int height;
private int fixedWidth; // set by setSize()
private int fixedHeight;
private Integer transparent = null; // transparent color if given
private int transIndex; // transparent index in color table
private int repeat = -1; // no repeat
private int delay = 0; // frame delay (hundredths)
private boolean started = false; // ready to output frames
private OutputStream out;
private Bitmap image; // current frame
private byte[] pixels; // BGR byte array from frame
private byte[] indexedPixels; // converted frame indexed to palette
private int colorDepth; // number of bit planes
private byte[] colorTab; // RGB palette
private boolean[] usedEntry = new boolean[256]; // active palette entries
private int palSize = 7; // color table size (bits-1)
private int dispose = -1; // disposal code (-1 = use default)
private boolean closeStream = false; // close stream when finished
private boolean firstFrame = true;
private boolean sizeSet = false; // if false, get size from first frame
private int sample = 10; // default sample interval for quantizer
private boolean hasTransparentPixels;
/**
* Sets the delay time between each frame, or changes it for subsequent frames
* (applies to last frame added).
*
* @param ms
* int delay time in milliseconds
*/
public void setDelay(int ms) {
delay = Math.round(ms / 10.0f);
}
/**
* Sets the GIF frame disposal code for the last added frame and any
* subsequent frames. Default is 0 if no transparent color has been set,
* otherwise 2.
*
* @param code
* int disposal code.
*/
public void setDispose(int code) {
if (code >= 0) {
dispose = code;
}
}
/**
* Sets the number of times the set of GIF frames should be played. Default is
* 1; 0 means play indefinitely. Must be invoked before the first image is
* added.
*
* @param iter
* int number of iterations.
*/
public void setRepeat(int iter) {
if (iter >= 0) {
repeat = iter;
}
}
/**
* Sets the transparent color for the last added frame and any subsequent
* frames. Since all colors are subject to modification in the quantization
* process, the color in the final palette for each frame closest to the given
* color becomes the transparent color for that frame. May be set to null to
* indicate no transparent color.
*
* @param color
* Color to be treated as transparent on display.
*/
public void setTransparent(int color) {
transparent = color;
}
/**
* Adds next GIF frame. The frame is not written immediately, but is actually
* deferred until the next frame is received so that timing data can be
* inserted. Invoking finish() flushes all frames. If
* setSize was invoked, the size is used for all subsequent frames.
* Otherwise, the actual size of the image is used for each frames.
*
* @param im
* BufferedImage containing frame to write.
* @return true if successful.
*/
public boolean addFrame(Bitmap im) {
return addFrame(im, 0, 0);
}
/**
* Adds next GIF frame to the specified position. The frame is not written immediately, but is
* actually deferred until the next frame is received so that timing data can be inserted.
* Invoking finish() flushes all frames. If setSize was invoked, the
* size is used for all subsequent frames. Otherwise, the actual size of the image is used for
* each frame.
*
* See page 11 of http://giflib.sourceforge.net/gif89.txt for the position of the frame
*
* @param im
* BufferedImage containing frame to write.
* @param x
* Column number, in pixels, of the left edge of the image, with respect to the left
* edge of the Logical Screen.
* @param y
* Row number, in pixels, of the top edge of the image with respect to the top edge of
* the Logical Screen.
* @return true if successful.
*/
public boolean addFrame(Bitmap im, int x, int y) {
if ((im == null) || !started) {
return false;
}
boolean ok = true;
try {
if (sizeSet) {
setFrameSize(fixedWidth, fixedHeight);
} else {
setFrameSize(im.getWidth(), im.getHeight());
}
image = im;
getImagePixels(); // convert to correct format if necessary
analyzePixels(); // build color table & map pixels
if (firstFrame) {
writeLSD(); // logical screen descriptor
writePalette(); // global color table
if (repeat >= 0) {
// use NS app extension to indicate reps
writeNetscapeExt();
}
}
writeGraphicCtrlExt(); // write graphic control extension
writeImageDesc(x, y); // image descriptor
if (!firstFrame) {
writePalette(); // local color table
}
writePixels(); // encode and write pixel data
firstFrame = false;
} catch (IOException e) {
ok = false;
}
return ok;
}
/**
* Flushes any pending data and closes output file. If writing to an
* OutputStream, the stream is not closed.
*/
public boolean finish() {
if (!started)
return false;
boolean ok = true;
started = false;
try {
out.write(0x3b); // GIF trailer
out.flush();
if (closeStream) {
out.close();
}
} catch (IOException e) {
ok = false;
}
// reset for subsequent use
transIndex = 0;
out = null;
image = null;
pixels = null;
indexedPixels = null;
colorTab = null;
closeStream = false;
firstFrame = true;
return ok;
}
/**
* Sets frame rate in frames per second. Equivalent to
* setDelay(1000/fps).
*
* @param fps
* float frame rate (frames per second)
*/
public void setFrameRate(float fps) {
if (fps != 0f) {
delay = Math.round(100f / fps);
}
}
/**
* Sets quality of color quantization (conversion of images to the maximum 256
* colors allowed by the GIF specification). Lower values (minimum = 1)
* produce better colors, but slow processing significantly. 10 is the
* default, and produces good color mapping at reasonable speeds. Values
* greater than 20 do not yield significant improvements in speed.
*
* @param quality int greater than 0.
*/
public void setQuality(int quality) {
if (quality < 1)
quality = 1;
sample = quality;
}
/**
* Sets the fixed GIF frame size for all the frames.
* This should be called before start.
*
* @param w
* int frame width.
* @param h
* int frame width.
*/
public void setSize(int w, int h) {
if (started) {
return;
}
fixedWidth = w;
fixedHeight = h;
if (fixedWidth < 1) {
fixedWidth = 320;
}
if (fixedHeight < 1) {
fixedHeight = 240;
}
sizeSet = true;
}
/**
* Sets current GIF frame size.
*
* @param w
* int frame width.
* @param h
* int frame width.
*/
private void setFrameSize(int w, int h) {
width = w;
height = h;
}
/**
* Initiates GIF file creation on the given stream. The stream is not closed
* automatically.
*
* @param os
* OutputStream on which GIF images are written.
* @return false if initial write failed.
*/
public boolean start(OutputStream os) {
if (os == null)
return false;
boolean ok = true;
closeStream = false;
out = os;
try {
writeString("GIF89a"); // header
} catch (IOException e) {
ok = false;
}
return started = ok;
}
/**
* Initiates writing of a GIF file with the specified name.
*
* @param file
* String containing output file name.
* @return false if open or initial write failed.
*/
public boolean start(String file) {
boolean ok = true;
try {
out = new BufferedOutputStream(new FileOutputStream(file));
ok = start(out);
closeStream = true;
} catch (IOException e) {
ok = false;
}
return started = ok;
}
/**
* Analyzes image colors and creates color map.
*/
private void analyzePixels() {
int len = pixels.length;
int nPix = len / 3;
indexedPixels = new byte[nPix];
NeuQuant nq = new NeuQuant(pixels, len, sample);
// initialize quantizer
colorTab = nq.process(); // create reduced palette
// convert map from BGR to RGB
for (int i = 0; i < colorTab.length; i += 3) {
byte temp = colorTab[i];
colorTab[i] = colorTab[i + 2];
colorTab[i + 2] = temp;
usedEntry[i / 3] = false;
}
// map image pixels to new palette
int k = 0;
for (int i = 0; i < nPix; i++) {
int index = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
usedEntry[index] = true;
indexedPixels[i] = (byte) index;
}
pixels = null;
colorDepth = 8;
palSize = 7;
// get closest match to transparent color if specified
if (transparent != null) {
transIndex = findClosest(transparent);
} else if (hasTransparentPixels) {
transIndex = findClosest(Color.TRANSPARENT);
}
}
/**
* Returns index of palette color closest to c
*
*/
private int findClosest(int color) {
if (colorTab == null)
return -1;
int r = Color.red(color);
int g = Color.green(color);
int b = Color.blue(color);
int minpos = 0;
int dmin = 256 * 256 * 256;
int len = colorTab.length;
for (int i = 0; i < len;) {
int dr = r - (colorTab[i++] & 0xff);
int dg = g - (colorTab[i++] & 0xff);
int db = b - (colorTab[i] & 0xff);
int d = dr * dr + dg * dg + db * db;
int index = i / 3;
if (usedEntry[index] && (d < dmin)) {
dmin = d;
minpos = index;
}
i++;
}
return minpos;
}
/**
* Extracts image pixels into byte array "pixels"
*/
private void getImagePixels() {
int w = image.getWidth();
int h = image.getHeight();
if ((w != width) || (h != height)) {
// create new image with right size/format
Bitmap temp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(temp);
canvas.drawBitmap(temp, 0, 0, null);
image = temp;
}
int[] pixelsInt = new int[w * h];
image.getPixels(pixelsInt, 0, w, 0, 0, w, h);
// The algorithm requires 3 bytes per pixel as RGB.
pixels = new byte[pixelsInt.length * 3];
int pixelsIndex = 0;
hasTransparentPixels = false;
int totalTransparentPixels = 0;
for (final int pixel : pixelsInt) {
if (pixel == Color.TRANSPARENT) {
totalTransparentPixels++;
}
pixels[pixelsIndex++] = (byte) (pixel & 0xFF);
pixels[pixelsIndex++] = (byte) ((pixel >> 8) & 0xFF);
pixels[pixelsIndex++] = (byte) ((pixel >> 16) & 0xFF);
}
double transparentPercentage = 100 * totalTransparentPixels / (double) pixelsInt.length;
// Assume images with greater where more than n% of the pixels are transparent actually have
// transparency. See issue #214.
hasTransparentPixels = transparentPercentage > MIN_TRANSPARENT_PERCENTAGE;
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "got pixels for frame with " + transparentPercentage
+ "% transparent pixels");
}
}
/**
* Writes Graphic Control Extension
*/
private void writeGraphicCtrlExt() throws IOException {
out.write(0x21); // extension introducer
out.write(0xf9); // GCE label
out.write(4); // data block size
int transp, disp;
if (transparent == null && !hasTransparentPixels) {
transp = 0;
disp = 0; // dispose = no action
} else {
transp = 1;
disp = 2; // force clear if using transparent color
}
if (dispose >= 0) {
disp = dispose & 7; // user override
}
disp <<= 2;
// packed fields
out.write(0 | // 1:3 reserved
disp | // 4:6 disposal
0 | // 7 user input - 0 = none
transp); // 8 transparency flag
writeShort(delay); // delay x 1/100 sec
out.write(transIndex); // transparent color index
out.write(0); // block terminator
}
/**
* Writes Image Descriptor
*/
private void writeImageDesc(int x, int y) throws IOException {
out.write(0x2c); // image separator
writeShort(x); // image position
writeShort(y);
writeShort(width); // image size
writeShort(height);
// packed fields
if (firstFrame) {
// no LCT - GCT is used for first (or only) frame
out.write(0);
} else {
// specify normal LCT
out.write(0x80 | // 1 local color table 1=yes
0 | // 2 interlace - 0=no
0 | // 3 sorted - 0=no
0 | // 4-5 reserved
palSize); // 6-8 size of color table
}
}
/**
* Writes Logical Screen Descriptor
*/
private void writeLSD() throws IOException {
// logical screen size
writeShort(width);
writeShort(height);
// packed fields
out.write((0x80 | // 1 : global color table flag = 1 (gct used)
0x70 | // 2-4 : color resolution = 7
0x00 | // 5 : gct sort flag = 0
palSize)); // 6-8 : gct size
out.write(0); // background color index
out.write(0); // pixel aspect ratio - assume 1:1
}
/**
* Writes Netscape application extension to define repeat count.
*/
private void writeNetscapeExt() throws IOException {
out.write(0x21); // extension introducer
out.write(0xff); // app extension label
out.write(11); // block size
writeString("NETSCAPE" + "2.0"); // app id + auth code
out.write(3); // sub-block size
out.write(1); // loop sub-block id
writeShort(repeat); // loop count (extra iterations, 0=repeat forever)
out.write(0); // block terminator
}
/**
* Writes color table
*/
private void writePalette() throws IOException {
out.write(colorTab, 0, colorTab.length);
int n = (3 * 256) - colorTab.length;
for (int i = 0; i < n; i++) {
out.write(0);
}
}
/**
* Encodes and writes pixel data
*/
private void writePixels() throws IOException {
LZWEncoder encoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
encoder.encode(out);
}
/**
* Write 16-bit value to output stream, LSB first
*/
private void writeShort(int value) throws IOException {
out.write(value & 0xff);
out.write((value >> 8) & 0xff);
}
/**
* Writes string to output stream
*/
private void writeString(String s) throws IOException {
for (int i = 0; i < s.length(); i++) {
out.write((byte) s.charAt(i));
}
}
}
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