将jpegs转换为gif太长
Converting jpegs to gifs is too long
我正试图用我从摄像机上得到的jpegs制作gif动画。但这个过程是不真实的漫长。我使用了两个不同的库。第一个是用原生C++代码编写的，第二个是Java的。
我尽可能压缩帧，但即使这样也不能减少生成时间。
原生库大约需要80-100秒，Java大约需要40-60秒（我不知道Java是怎么快2倍的，但日志显示了这个结果），5秒的视频每秒16帧（每gif 80帧）。
我根据这个修改了一个位C++算法，因为我遇到了同样的问题（尝试了两个版本，分别修改了一段代码和整个learn()函数）。
在这里你可以看到一段日志：
它是本机实现中的最后三个框架：
D/TimeUtils: Adding frame executed in 949ms
D/TimeUtils: Adding frame executed in 976ms
D/TimeUtils: Adding frame executed in 1028ms
D/TimeUtils: Creating gif with native library executed in 82553ms
这是Java版本中的最后三个帧：
D/TimeUtils: Adding frame executed in 541ms
D/TimeUtils: Adding frame executed in 513ms
D/TimeUtils: Adding frame executed in 521ms
D/TimeUtils: Creating gif with nbadal's library executed in 44811ms
也许还有其他一些有用的日志：
D/CameraActivity: Duration of the captured video is 5000ms
V/CameraActivity: Dimensions are 288w x 288h
D/CameraActivity: Final bitmaps count: 80
TimeUtils.java包含用于检查方法执行时间的静态方法。
NativeGifConverter.java（仅转换函数）：
@Override public void createGifFile(String path, List<String> bitmapPaths) {
Bitmap bitmap = BitmapUtils.retrieve(bitmapPaths.get(0));
if (init(path, bitmap.getWidth(), bitmap.getHeight(), mNumColors, mQuality, mFrameDelay) != 0) {
Timber.e("Gifflen init failed");
return;
}
bitmap.recycle();
for (String bitmapPath : bitmapPaths) {
bitmap = howLong("Retrieving bitmap", () -> BitmapUtils.retrieve(bitmapPath));
final int width = bitmap.getWidth();
final int height = bitmap.getHeight();
final int[] pixels = new int[width * height];
final Bitmap finalBitmap = bitmap; // for counting time
howLongVoid("Retrieving pixels", () -> finalBitmap.getPixels(pixels, 0, width, 0, 0, width, height));
howLongVoid("Adding frame", () -> addFrame(pixels));
bitmap.recycle();
}
bitmap = null;
close();
}
NbadalGifConverter.java（仅转换函数）：
@Override public void createGifFile(String path, List<String> bitmapsNames) {
final ByteArrayOutputStream bos = new ByteArrayOutputStream();
final AnimatedGifEncoder encoder = new AnimatedGifEncoder();
encoder.setDelay(mDelay);
encoder.setQuality(mQuality);
encoder.start(bos);
for (String bitmapName : bitmapsNames) {
final Bitmap bitmap = howLong("Retrieving bitmap", () -> BitmapUtils.retrieve(bitmapName));
howLongVoid("Adding frame", () -> encoder.addFrame(bitmap));
}
encoder.finish();
FileUtils.store(bos.toByteArray(), path.substring(0, path.lastIndexOf('.')) + ".gif");
}
我愿意向您展示另一段相关的代码。如果有任何帮助，我将不胜感激。
[更新]
检索位图的日志：
D/TimeUtils: Retrieving bitmap executed in 3ms
D/TimeUtils: Retrieving bitmap executed in 3ms
D/TimeUtils: Retrieving bitmap executed in 4ms
首先，我要感谢@Spektre的回答：有效的gif/图像颜色量化？
我和我的同事刚刚把它从C++翻译成Java。它在4倍的时间内显示出良好的效果。我会尝试改进它，但这已经是比AnimatedGifEncoder.java（我以前用过）更好的结果了
这是代码：
public static final int MAX_COLOR_COUNT = 65536;
/**
* @param pixels rgb 888
* @param palette int[256]
* @return indices of colors in palette
*/
private int[][][] createPalette(int[] pixels, int[] palette) {
final int[] histogram = new int[MAX_COLOR_COUNT]; // pixel count histogram
final int[] indices = new int[MAX_COLOR_COUNT]; // here index is color value
for (int i = 0; i < MAX_COLOR_COUNT; i++) {
indices[i] = i;
}
// creating histogram
for (int color : pixels) {
// 0001 1111 0111 1110 0000 1111 1000 0000 0000
color = ((color >> 3) & 0x1F) | ((color >> 5) & 0x7E0) | ((color >> 8) & 0xF800);
if (histogram[color] < Integer.MAX_VALUE) { // picture must be really big
histogram[color]++;
}
}
// removing zeros
int j = 0;
for (int i = 0; i < MAX_COLOR_COUNT; i++) {
histogram[j] = histogram[i];
indices[j] = indices[i];
if (histogram[j] != 0) {
j++;
}
}
final int histograms = j;
// bubble sort
for (int i = 1; i != 0; ) {
i = 0;
for (int x = 0, y = 1; y < histograms; x++, y++) {
if (histogram[x] < histogram[y]) {
i = histogram[x];
histogram[x] = histogram[y];
histogram[y] = i;
i = indices[x];
indices[x] = indices[y];
indices[y] = i;
i = 1;
}
}
}
final int[][][] colorMap = new int[32][64][32];
int colorTableIndex = 0, x = 0;
for (; x < histograms; x++) { // main colors
final int color = indices[x];
// 1f (16) = 0001 1111 (2)
// 3f (16) = 0011 1111 (2)
// (1111 1)(111 111)(1 1111)
final int b = color & 0x1f;
final int g = (color >> 5) & 0x3f;
final int r = (color >> 11) & 0x1f;
// skip if similar color already in palette[]
int a = 0, i = 0;
for (; i < colorTableIndex; i++) {
final byte tempB = (byte) ((palette[i] >> 3) & 0x1f);
final byte tempG = (byte) ((palette[i] >> 10) & 0x3f);
final byte tempR = (byte) ((palette[i] >> 19) & 0x1f);
// if difference between two colors is pretty small
// taxicab distance
int difference = tempB - b;
if (difference < 0) {
difference = -difference;
}
a = difference;
difference = tempG - g;
if (difference < 0) {
difference = -difference;
}
a += difference;
difference = tempR - r;
if (difference < 0) {
difference = -difference;
}
a += difference;
if (a <= 2) { // smaller than 16/8
a = 1;
break;
}
a = 0;
}
if (a != 0) {
colorMap[r][g][b] = i; // map to existing color
} else {
colorMap[r][g][b] = colorTableIndex; // map to new index
// 1111 1000 1111 1100 1111 1000
palette[colorTableIndex] = b << 3 | (g << 10) | (r << 19); // fill this index with new color
colorTableIndex++;
if (colorTableIndex >= 256/*palette.length*/) {
x++;
break;
}
}
} // colorTableIndex = new color table size
for (; x < histograms; x++) { // minor colors
final int color = indices[x];
final int b = color & 0x1f;
final int g = (color >> 5) & 0x3f;
final int r = (color >> 11) & 0x1f;
// find closest color
int minDistance = -1;
int colorIndex = 0;
for (int a, i = 0; i < colorTableIndex; i++) {
final byte tempB = (byte) ((palette[i] >> 3) & 0x1f);
final byte tempG = (byte) ((palette[i] >> 10) & 0x3f);
final byte tempR = (byte) ((palette[i] >> 19) & 0x1f);
int difference = tempB - b;
if (difference < 0) {
difference = -difference;
}
a = difference;
difference = tempG - g;
if (difference < 0) {
difference = -difference;
}
a += difference;
difference = tempR - r;
if (difference < 0) {
difference = -difference;
}
a += difference;
if ((minDistance < 0) || (minDistance > a)) {
minDistance = a;
colorIndex = i;
}
}
colorMap[r][g][b] = colorIndex;
}
return colorMap;
}
private byte[] map(int[] pixels, int[][][] colorMap) {
final int pixelsLength = pixels.length;
final byte[] mapped = new byte[pixelsLength];
for (int i = 0; i < pixelsLength; i++) {
final int color =
((pixels[i] >> 3) & 0x1F) | ((pixels[i] >> 5) & 0x7E0) | ((pixels[i] >> 8) & 0xF800);
final int b = color & 0x1f;
final int g = (color >> 5) & 0x3f;
final int r = (color >> 11) & 0x1f;
mapped[i] = (byte) colorMap[r][g][b];
}
return mapped;
}
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