NGif, Animated GIF Encoder for .NET

In the LZWEncoder remove remaining and replace NextPixel():

private int NextPixel()
{
if (curPixel == pixAry.Length) return EOF;
curPixel++;
return pixAry[curPixel - 1] & 0xff;
}

Thank YOU for this FIX. It saved hours.... Thumbs Up | :thumbsup:

Very nice work on the library. Here is a VB.NET version of it, in case anyone is thinking of using it in VB.NET:

http://www.programmingtalk.com/showpost.php?p=150213&postcount=4[^]

Pete Soheil
DigiOz Multimedia
http://www.digioz.com

the original Gif File size is 9K
Use Gif.Components.GifDecoder() then Gif.Components.AnimatedGifEncoder() merge.
the result Gif file size be changed to 11K

why?

I am also facing the same problem. my original image is 19k animated gif.

using the code I decoded it into frames and combined together. But the new image size varies from 67 to 77 baesd on the image quality set

have some problem with this ,i m currently working on same application where animated image is resized but problem is that, i have completed reading of animation , i have done resizing of static images and creating of new animated images but problem is there , wen i want to combine all together, can anyone help me , if u have any relevant info,plz reply me

-- modified at 4:16 Monday 5th November, 2007

what is the problem u are facing when combining the frames?

Need to modify two methods in GifDecoder.cs:

int [] GetPixels( Bitmap bitmap )
{
int [] pixels = new int [image.Width * image.Height];
int count = 0;
for (int th = 0; th < image.Height; th++)
{
for (int tw = 0; tw < image.Width; tw++)
{
Color color = bitmap.GetPixel(tw, th);
pixels[count++] = color.ToArgb();
}
}
return pixels;
}

protected void SetPixels()
{
// expose destination image's pixels as int array
// int[] dest =
// (( int ) image.getRaster().getDataBuffer()).getData();
//int[] dest = GetPixels( bitmap );

int[] dest = null;

// fill in starting image contents based on last image's dispose code
if (lastDispose > 0)
{
if (lastDispose == 3)
{
// use image before last
int n = frameCount - 2;
if (n > 0)
{
lastImage = GetFrame(n - 1);
}
else
{
lastImage = null;
}
}
if (lastImage != null)
{
if (lastDispose == 2)
{
// fill last image rect area with background color
lastImage = new Bitmap(lastImage);
Graphics g = Graphics.FromImage(lastImage);
Color c = Color.Empty;
if (transparency)
{
c = Color.FromArgb(255, 0, 0, 0); // assume background is transparent
}
else
{
c = Color.FromArgb( lastBgColor ) ;
// c = new Color(lastBgColor); // use given background color
}
Brush brush = new SolidBrush( c );
g.FillRectangle( brush, lastRect );
brush.Dispose();
g.Dispose();
}
dest = GetPixels((Bitmap)lastImage);
}
}

if (dest == null) dest = new int[bitmap.Width * bitmap.Height];

// 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 < ih; i++)
{
int line = i;
if (interlace)
{
if (iline >= ih)
{
pass++;
switch (pass)
{
case 2 :
iline = 4;
break;
case 3 :
iline = 2;
inc = 4;
break;
case 4 :
iline = 1;
inc = 2;
break;
}
}
line = iline;
iline += inc;
}
line += iy;
if (line < height)
{
int k = line * width;
int dx = k + ix; // start of line in dest
int dlim = dx + iw; // end of dest line
if ((k + width) < dlim)
{
dlim = k + width; // past dest edge
}
int sx = i * iw; // start of line in source
while (dx < dlim)
{
// map color and insert in destination
int index = ((int) pixels[sx++]) & 0xff;
int c = act[index];
if (c != 0)
{
dest[dx] = c;
}
dx++;
}
}
}
SetPixels( dest );
}

I am also try to use LockBits in GetPixels and SetPixels, without using unsafe code. I have found a way, but need some time to finish it.

Can you please let all know what the bug actually is ?

Thanks
A

Could you please send me your latest copy of this project? I'm in great need of it now, thanks a lot~
My e-mail is cmhienng1983@hotmail.com Smile | :)

cmhienng

Hello,

Can you please send your updated project to me at xzhang@dewberry.com?
Thanks a lot,

xiaoyi zhang
Dewberry

I've tried settign a value for the transparency but no matter what I do it doesn't work. I noticed that the FindClosest function called in Save() was beign called before the Analyze function. I updated the code so that FindClosest now returns what looks like an accurate index as far as I can tell but when I look at th eGif in IE then the transparency is not showing (excuse the 'pun') and in a Gif editor the transparency is not set.

Has anyone else tried using the transparency in this? I really want to avoid sitting down and reading the enitre Gif Spec to understand this!

Thanks in advance

Jim

Hi,

I have found this problem. To fix it:

edit file AnimatedGifEncoder.cs, at the end of the method AnalyzePixels(), comment Findcloasest, instead, using nq.Map:

// transIndex = FindClosest(transparent);
transIndex = nq.Map(transparent.B, transparent.G, transparent.R);

It will work.

I also fixed a number of other bugs in GifDecoder.cs. I want to post the whole package up, but don't know how.

Adam

Hi
Can you please email the complete code at angel1241@hotmail.com?

Thanks
A

Hi Chuanchu:

Could you please also send me a copy of your bug-fixing copy. I will appreciate it very much!

Jeff Tan
x.tan@hotmail.com

i tried this.
I am facing problem with transparent images in decoding itself(while splitting)
I am geting the first frame with transparent background but the rest is geting a black background

Hi,

Your fix so nearly almost worked! The bottom-right pixel of the resulting animation appears to flicker through a selection of colours. Any ideas on how to fix this?

Edit: I've just also noticed parts of the image becoming transparent which weren't originally transparent. I'm guessing this is something to do with the colour of those parts matching the transparency colour. Does this mean having to write an algorithm to find an unused colour in all frames prior to adding them?

Nope. Still doesn't work. Anyone find a solution to this problem?

hello can you please email me updated bugs free file of this example on my email id ..its arpit@sleexs.com

Thank you in advance

I have use the code on the Net CF 1.0. and Found it does not pharse the gif file well.
When I fixed the follow code, it work well now.
I just modify the function GetPixels in the file GifDecoder
int [] GetPixels( Bitmap bitmap )
{
//int [] pixels = new int [ 3 * image.Width * image.Height ]; //Orginal
int[] pixels = new int[3 * image.Width * image.Height]; //Modified
int count = 0;
for (int th = 0; th < image.Height; th++)
{
for (int tw = 0; tw < image.Width; tw++)
{
Color color = bitmap.GetPixel(tw, th);
// pixels[count] = color.R; //Orginal
// count++; //Orginal
// pixels[count] = color.G;//Orginal
// count++;//Orginal
// pixels[count] = color.B;//Orginal
pixels[count] = color.ToArgb(); //Added
count++;
}
}
return pixels;

Would anyone please confirm it?

Good work. However this line should be
//int[] pixels = new int[3 * image.Width * image.Height]; //Modified
int[] pixels = new int[image.Width * image.Height]; // New Modified

Smile | :)

This WORKED. NICE Job! Smile | :)

I looked all over the NET. This by far is the only good enough solution I see (even in April 2007) -- full 2 years after this article was written.

The only thing I would want to change in this code would be to optimize for speed and size; nothing else!

I have been able to optimize the GifDecoder quiet a bit, but at the expense of compatability. The realy slow code which runs a lot (realy A LOT) of times is the GetPixel() and SetPixel() functions. I have rewritten the code to avoid the use of those, but this have to be done in "usafe" context. This means that you have to compile with the compiler option "unsafe", and that the executable will only run on the processor type you compiled it on (afair). You can just replace the two functions below in the GifDecoder.cs file.
Here is the code for the GetPixels function

int [] GetPixels( Bitmap bitmap )
{
	int [] pixels = new int [ 3 * image.Width * image.Height ];
	int count = 0;
    int tw, th;

    BitmapData data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, bitmap.PixelFormat);
    int scanwidth = data.Stride;
    System.IntPtr Scan = data.Scan0;
    int width = bitmap.Width;
    int height = bitmap.Height;

    unsafe
    {
        int offset; // excess pixels at each row, to counter word alignment
        if (bitmap.PixelFormat == PixelFormat.Format32bppArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppPArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppRgb)
        {
            offset = scanwidth - bitmap.Width * 4;
        }
        else // assume 24 bits per pixel
            offset = scanwidth - bitmap.Width * 3; 
        int x, y;
        byte colr, colg, colb;
        byte* p = (byte*)(void*)Scan;
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                pixels[count++] = (int)*(p++);
                pixels[count++] = (int)*(p++);
                pixels[count++] = (int)*(p++);
            }
            p += offset;
        }
    } // End of unsafe
    bitmap.UnlockBits(data);
	return pixels;
}

Here is the code for the SetPixels function

void SetPixels( int [] pixels )
{
	int count = 0;

    BitmapData data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadWrite, bitmap.PixelFormat);
    int scanwidth = data.Stride;
    System.IntPtr Scan = data.Scan0;
    int width = image.Width;
    int height = image.Height;
    unsafe
    {
        bool fourBytePerPixel = false;
        int offset; // excess pixels at each row, to counter word alignment
        if (bitmap.PixelFormat == PixelFormat.Format32bppArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppPArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppRgb)
        {
            offset = scanwidth - bitmap.Width * 4;
            fourBytePerPixel = true;
        }
        else // assume 24 bits per pixel
            offset = scanwidth - bitmap.Width * 3;
        int x, y;
        byte* p = (byte*)(void*)Scan;
        Int32 pixeldata;
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                pixeldata = pixels[count++];

                *(p++) = (byte)(pixeldata);
                *(p++) = (byte)(pixeldata >> 8);
                *(p++) = (byte)(pixeldata >> 16);
                if (fourBytePerPixel)
                    *(p++) = (byte)(pixeldata >> 24);
            }
            p += offset;
        }
    } // End of unsafe
    bitmap.UnlockBits(data);
}

You must have me excused if the code is a bit cluttered, but it should be usefull anyway. Actually I have not gone into details to see whether it is necessary to test for 24 or 32 bit images, as the code might use purly 32 bit images.

- Lothver

Has anyone been able to optimize this code for the encoder?

I have 15 frames which amount to 82kb, however if I use a animated gif application its only 38kb, something isn't right?

modified 19-Aug-21 21:01pm.

NGif, Animated GIF Encoder for .NET

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