I need to load GIF animations and convert them frame by frame to bitmaps. To do that, I am extracting my GIF file frame by frame using Drawing.Imaging library and then casting each frame to bitmap.
Everything works just fine except the times when the consecutive frames are the same, when there is no pixel difference. The library seems to be dropping such frames.
I came to that conslusion with a simple test. I have created an animation of a circle that is growing and shrinking with a pause between the moment the last circle dissapears and the new one is not yet shown. When I play the animation consisting of my extracted bitmaps that pause is not present. If I compare the GIFs of the same frame-length but different amounts of identical frames, the returned totalframescount value is different. I have also observed that webbrowsers display identical consecutive frames correctly.
public void DrawGif(Image img)
{
FrameDimension dimension = new FrameDimension(img.FrameDimensionsList[0]);
int frameCountTotal = img.GetFrameCount(dimension);
for (int framecount = 0; framecount < frameCountTotal; framecount++)
{
img.SelectActiveFrame(dimension, framecount);
Bitmap bmp = new Bitmap(img); //cast Image type to Bitmap
for (int i = 0; i < 16; i++)
{
for (int j = 0; j < 16; j++)
{
Color color = bmp.GetPixel(i, j);
DrawPixel(i, j, 0, color.R, color.G, color.B);
}
}
- Does someone encountered such a problem?
- As I am pretty new to C# - is there a way to modify .NET lib ?
- Maybe there is a solution to my problem that I am not aware of, that does not involve changing the library?
Updated code - the result is the same
public void DrawGif(img)
{
int frameCountTotal = img.GetFrameCount(FrameDimension.Time);
for (int framecount = 0; framecount < frameCountTotal; framecount++)
{
img.SelectActiveFrame(FrameDimension.Time, framecount);
Bitmap bmp = new Bitmap(img);
for (int i = 0; i < 16; i++)
{
for (int j = 0; j < 16; j++)
{
Color color = bmp.GetPixel(i, j);
DrawPixel(i, j, 0, color.R, color.G, color.B);
}
The
Image
is not saving duplicate frames, so you have to take the time of each frame into account. Here is some sample code based on this book in Windows Programming on how to get all the frames and the correct duration. An example:We need a structure to save the Bitmap and duration for each Frame
The code will load a
Bitmap
, check whether it is a multi-frame animatedGIF
. It then loops though all the frames to construct a list of separateFrame
objects that hold the bitmap and duration of each frame. Simple use: