charlietangora / gif-h Goto Github PK

I wrote only white (255, 255, 255) and blue (0, 0, 255) colors, using SetPixel, and the resultant file shows up in white and green. =/

Hi Charlie,

I've implemented a c++ class based on this project, gif-h.

You can find it here. Feel free to link to it, etc.; I have of course linked my project to yours.

Also, credit is given here.

Thanks so much for your work. Much appreciated!

it is possible that treeRoot in GifGetClosestPaletteColor becomes 255.
Put an assert(treeRoot < 255) into line 110 if you want to validate that statement.
In line 113, treeRoot is used as index into GifPalette::treeSplitElt, which is a statically allocated array of size 255.
This, of course, yields to a buffer overflow.

Most of the time it goes well, it did crash yet. But it's a bug and it cost me 2 days to spot (no offense).
I guess it can be fixed easily by changing the size of the two GifPalette::treeSplit*-arrays to 256 (maybe the 255 is a typo?)

(I'm working on a PR)

I'm generating a gif from an OpenGL application, which has a bottom-left based coordinate system, which means my gifs all come out upside down.

Whilst it's straightforward enough to flip the buffer myself before passing it to GifWriteFrame it seems like it would be massively more efficient for the encoder to just know to read the pixels "backwards" so to speak - is there a simple place I could change this to be able to pass a "flip vertically" flag through the whole code?

Any help would be appreciated. I am trying to convert a video to GIF using OpenCV. Gif output is weird.

Here is the code

    cv::Mat frame;

    GifWriter writer;

    bool success = video.read(frame);

    GifBegin(&writer, destFile.c_str(), frame.size().width, frame.size().height, 20);

    uint frameCounter = 0;

    while(success && frameCounter<=15){

        success = video.read(frame);

        GifWriteFrame(&writer,frame.data, frame.size().width, frame.size().height, 20);

        frameCounter++;

    }

    GifEnd(&writer);

    video.release();

Thanks

GifWriteFrame the GIF size is too big, how to use GifWriteLzwImage ?

Hi, I would like to use gif-h on raylib to add simple .gif export functionality. That would be very useful for students to show and share their small games. Right now raylib offers automatic screenshot generation just pressing F12, some animated image would be great.

I tried it, exporting every 10 frames, and it works ok (maybe a bit slow...) but raylib is C99 and to include gif-h it requires to be compiled as C++, it's not a big deal but it should be C99 to be included in the library.

Also, would it be possible to adapt library to header-only style like STB libraries, I mean with GIF_IMPLEMENTATION define?

The following simple program creates a GIF composed of two completely white frames. But Valgrind's Memcheck complains about an uninitialized memory in GifBegin().

#include "gif.h"

static const int width = 200;
static const int height = 200;

static uint8_t image[width * height * 4];

int main(int argc, char* argv[])
{
  const char* filename = "mytest.gif";
  if (argc > 1) {
    filename = argv[1];
  }

  GifWriter writer;
  GifBegin(&writer, filename, width, height, 100);

  for (int i = 0; i < sizeof image; i += 4) {
    image[i] = image[i + 1] = image[i + 2] = 255;
    image[i + 3] = 0;  // not necessary
  }
  GifWriteFrame(&writer, image, width, height, 100);
  GifWriteFrame(&writer, image, width, height, 100);

  GifEnd(&writer);
  return 0;
}

mymedia@barberry:~/src/gif-h$ valgrind ./a.out 
==98249== Memcheck, a memory error detector
==98249== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==98249== Using Valgrind-3.17.0 and LibVEX; rerun with -h for copyright info
==98249== Command: ./a.out
==98249== 
==98249== Syscall param write(buf) points to uninitialised byte(s)
==98249==    at 0x49809B7: write (write.c:26)
==98249==    by 0x48F7E6C: _IO_file_write@@GLIBC_2.2.5 (fileops.c:1181)
==98249==    by 0x48F9970: new_do_write (fileops.c:449)
==98249==    by 0x48F9970: _IO_new_do_write (fileops.c:426)
==98249==    by 0x48F9970: _IO_do_write@@GLIBC_2.2.5 (fileops.c:423)
==98249==    by 0x48F8F67: _IO_file_close_it@@GLIBC_2.2.5 (fileops.c:136)
==98249==    by 0x48EBE0E: fclose@@GLIBC_2.2.5 (iofclose.c:53)
==98249==    by 0x10B744: GifEnd(GifWriter*) (gif.h:827)
==98249==    by 0x10B8D1: main (mytest.c:25)
==98249==  Address 0x4abb837 is 1,175 bytes inside a block of size 4,096 alloc'd
==98249==    at 0x4843839: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==98249==    by 0x48EBC23: _IO_file_doallocate (filedoalloc.c:101)
==98249==    by 0x48FAC6F: _IO_doallocbuf (genops.c:347)
==98249==    by 0x48F9EFF: _IO_file_overflow@@GLIBC_2.2.5 (fileops.c:745)
==98249==    by 0x48F8694: _IO_new_file_xsputn (fileops.c:1244)
==98249==    by 0x48F8694: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1197)
==98249==    by 0x48ED066: fwrite (iofwrite.c:39)
==98249==    by 0x10B342: GifBegin(GifWriter*, char const*, unsigned int, unsigned int, unsigned int, int, bool) (gif.h:754)
==98249==    by 0x10B7DD: main (mytest.c:16)
==98249== 
==98249== 
==98249== HEAP SUMMARY:
==98249==     in use at exit: 0 bytes in 0 blocks
==98249==   total heap usage: 7 allocs, 7 frees, 4,678,872 bytes allocated
==98249== 
==98249== All heap blocks were freed -- no leaks are possible
==98249== 
==98249== Use --track-origins=yes to see where uninitialised values come from
==98249== For lists of detected and suppressed errors, rerun with: -s
==98249== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Hello! I have been trying to use gif.h for GIF recording in my application. Long story short, it works, with one flaw. The first frame is the only one kept. Here is a sample result:

The code I used is available here:

QImage &startImg = frames[0];
GifWriter writer;
GifBegin(&writer, tmpDir.absoluteFilePath("resulting.gif").toLocal8Bit().constData(), startImg.width(),
startImg.height(), d);
int i = 0;
for (QImage &a : frames) {
    QByteArray alpha8((char *)a.bits(), a.byteCount());
    GifWriteFrame(&writer, (uint8_t *)alpha8.data(), a.width(), a.height(), d);
}
GifEnd(&writer);

Thanks in advance!