我有一段代码可以调整GIF动画的大小。 如果它有助于代码将始终将图像调整为较小的大小。 （现在没有必要让它们变大）
我正在使用Atalasoft的dotimage库及其示例代码来进行实际重新采样。 该代码应该从磁盘读取动画gif，迭代帧并将每个帧的大小调整为新的大小。 当gif动画包含相同大小的帧时，这可以正常工作，但是调整具有不同大小的帧的动画会破坏动画（在调整大小后帧不会正确地相互重叠），我认为这是因为代码不计算新的偏移量正确。
我认为正是这行代码没有正确计算偏移量： Point point = new Point（（int）（frame.Location.X * ratio），（int）（frame.Location.Y * ratio））;
这是完整的调整大小例程：
static private void GenerateGifImage(FileStream fileStream, int OutputWidth, int OutputHeight)
{
// MemoryStream InputStream = new MemoryStream();
FileStream InputStream = fileStream;
// fileStream.Write(InputStream.GetBuffer(), 0, (int)InputStream.Position);
// InputStream.Seek(0, SeekOrigin.Begin);
Image InputImage = Image.FromStream(InputStream, true, false);
// this will invalidate the underlying image object in InputImage but the class properties
// will still accessible until the object is disposed
InputStream.Seek(0, SeekOrigin.Begin);
ImageInfo imageInfo = RegisteredDecoders.GetImageInfo(InputStream);
InputStream.Seek(0, SeekOrigin.Begin);
GifDecoder gifDecoder = new GifDecoder();
int count = gifDecoder.GetFrameCount(InputStream);
GifFrameCollection gifFrameCollection = new GifFrameCollection();
gifFrameCollection.Height = OutputHeight;
gifFrameCollection.Width = OutputWidth;
// gifFrameCollection.Height = gifDecoder.Frames.Height;
// gifFrameCollection.Width = gifDecoder.Frames.Width;
double ratio;
if (InputImage.Height > InputImage.Width)
{
ratio = (double)OutputHeight / (double)InputImage.Height;
}
else
{
ratio = (double)OutputWidth / (double)InputImage.Width;
}
for (int i = 0; i < count; i++)
{
GifFrame frame = gifDecoder.Frames[i];
Rectangle rectangle = new Rectangle(Point.Empty, frame.Image.Size);
int frameWidth = (int)(frame.Image.Width * ratio);
int frameHeight = (int)(frame.Image.Height * ratio);
// account for erratic rounding, seems illogical but has happened earlier when using floats instead of doubles
if (frameWidth > OutputWidth)
{
frameWidth = OutputWidth;
}
if (frameHeight > OutputHeight)
{
frameHeight = OutputHeight;
}
Size size = new Size(frameWidth, frameHeight);
// only resize if we have a measureable dimension
if (size.Width > 0 && size.Height > 0)
{
// ResampleCommand resampleCommand = new ResampleCommand(rectangle, size, ResampleMethod.NearestNeighbor);
ResampleCommand resampleCommand = new ResampleCommand(rectangle, size, ResampleMethod.NearestNeighbor);
AtalaImage atalaImage = resampleCommand.Apply(frame.Image).Image;
// save the image for debugging
// atalaImage.Save("frame" + i.ToString() + ".gif", ImageType.Gif, null);
// frame.Image.Save("frame-orig" + i.ToString() + ".gif", ImageType.Gif, null);
// AtalaImage atalaImage = frame.Image;
Point point = new Point((int)(frame.Location.X * ratio), (int)(frame.Location.Y * ratio));
// Point point = new Point((int)(frame.Location.X), (int)(frame.Location.Y));
gifFrameCollection.Add(new GifFrame(atalaImage, point, frame.DelayTime, frame.Interlaced, frame.FrameDisposal, frame.TransparentIndex, frame.UseLocalPalette));
}
}
FileStream saveStream = new FileStream("resized.gif", FileMode.Create, FileAccess.Write, FileShare.Write);
GifEncoder gifSave = new GifEncoder();
gifSave.Save(saveStream, gifFrameCollection, null);
saveStream.Close();
}
答案 0 :(得分：1)
我在Atalasoft工作
我调查了这个 - 你的代码是完全正确的，并且可以在不同大小的帧上工作。你计算的点是正确的。
问题在于，在你的3帧GIF中，你的第二帧和第三帧被精确地叠加在第一帧之上，并使用非常复杂的透明蒙版来显示第一帧。当您的图像重新采样到新的大小时，蒙版可能不再精确 - 因为您要调整宽度和高度上只有一个像素差异，所以此蒙版无法匹配。
这个问题有几种解决方案
我为你编写了＃3 - 它运作良好
static private void GenerateGifImage(FileStream fileStream, int OutputWidth, int OutputHeight)
{
// MemoryStream InputStream = new MemoryStream();
FileStream InputStream = fileStream;
// fileStream.Write(InputStream.GetBuffer(), 0, (int)InputStream.Position);
// InputStream.Seek(0, SeekOrigin.Begin);
Image InputImage = Image.FromStream(InputStream, true, false);
// this will invalidate the underlying image object in InputImage but the class properties
// will still accessible until the object is disposed
InputStream.Seek(0, SeekOrigin.Begin);
ImageInfo imageInfo = RegisteredDecoders.GetImageInfo(InputStream);
InputStream.Seek(0, SeekOrigin.Begin);
GifDecoder gifDecoder = new GifDecoder();
int count = gifDecoder.GetFrameCount(InputStream);
GifFrameCollection gifFrameCollection = new GifFrameCollection();
gifFrameCollection.Height = OutputHeight;
gifFrameCollection.Width = OutputWidth;
double ratio;
if (InputImage.Height > InputImage.Width)
{
ratio = (double)OutputHeight / (double)InputImage.Height;
}
else
{
ratio = (double)OutputWidth / (double)InputImage.Width;
}
for (int i = 0; i < count; i++)
{
GifFrame frame = gifDecoder.Frames[i];
Rectangle rectangle = new Rectangle(Point.Empty, frame.Image.Size);
int newframeWidth = frame.Image.Width;
int newframeHeight = frame.Image.Height;
if (newframeWidth > OutputWidth || newframeHeight > OutputHeight)
{
newframeWidth = (int)(frame.Image.Width * ratio);
newframeHeight = (int)(frame.Image.Height * ratio);
}
// account for erratic rounding, seems illogical but has happened earlier when using floats instead of doubles
if (newframeWidth > OutputWidth)
{
newframeWidth = OutputWidth;
}
if (newframeHeight > OutputHeight)
{
newframeHeight = OutputHeight;
}
Size size = new Size(newframeWidth, newframeHeight);
// only resize if we have a measureable dimension
if (size.Width > 0 && size.Height > 0)
{
//ResampleCommand resampleCommand = new ResampleCommand(rectangle, size, ResampleMethod.);
AtalaImage atalaImage = frame.Image;
if (newframeWidth != frame.Image.Width || newframeHeight != frame.Image.Height)
{
CropCommand command = new CropCommand(new Rectangle(new Point(0, 0), size));
atalaImage = command.Apply(frame.Image).Image;
}
// AtalaImage atalaImage = frame.Image;
Point point = new Point((int)(frame.Location.X), (int)(frame.Location.Y));
// Point point = new Point((int)(frame.Location.X), (int)(frame.Location.Y));
gifFrameCollection.Add(new GifFrame(atalaImage, point, frame.DelayTime, frame.Interlaced, frame.FrameDisposal, frame.TransparentIndex, frame.UseLocalPalette));
}
}
FileStream saveStream = new FileStream("resized.gif", FileMode.Create, FileAccess.Write, FileShare.Write);
GifEncoder gifSave = new GifEncoder();
gifSave.Save(saveStream, gifFrameCollection, null);
saveStream.Close();
}
答案 1 :(得分：0)
如果您使用不同的帧大小，则计算的比率值不正确。您应该计算每个帧的比率，以便您关注的线使用正确的比率。我不熟悉这个框架，所以我不能给你一个准确的例子;但它看起来应该类似于：
GifFrame frame = gifDecoder.Frames[i];
double frameRatio;
if (frame.Height > frame.Width)
{
frameRatio = (double)OutputHeight / (double)frame.Height;
}
else
{
frameRatio = (double)OutputWidth / (double)frame.Width;
}
...
Point point = new Point((int)(frame.Location.X * frameRatio), (int)(frame.Location.Y * frameRatio));