public void AddColorTable(ColorTable colortable)
{
m_ctables.Add(colortable);
}
protected override void LoadImage()
{
m_bitsPerPixel = 8;
m_isTransparent = false;
m_colorSpace = new ColorSpace();
ColorSpace.AddDevice(ColorDevice.Indexed);
ColorSpace.AddDevice(ColorDevice.DeviceRGB);
//add the LZW filter
m_filter = new LZWFilter(); //migth need some parameters! '/EarlyChange' for instance
var ImageHolder = new FileStream(m_href, FileMode.Open, FileAccess.Read, FileShare.Read, 8192);
var len = (int) ImageHolder.Length;
var buf = new byte[len + 1]; //the +1 is a dirty hack , don't like it
ImageHolder.Read(buf, 0, len);
var state = gif_states.gif_init;
var colorTableSize = 0;
var p = 0;
while (true)
{
switch (state)
{
case gif_states.gif_init:
if (buf[0] != 0x47 || buf[1] != 0x49 || buf[2] != 0x46)
throw new ImageFormatException("Invalid GIF format : No a GIF file.");
/// p = 6 ; // version ~ uninsteresting
m_width = toShortInverted(buf[6], buf[7]);
m_height = toShortInverted(buf[8], buf[9]);
byte packed_field = buf[10];
colorTableSize = 2 << (packed_field & 0x07);
//byte 11: Background Color Index
//byte 12: Pixel Aspect Ratio
p = 13;
state = (packed_field & 0x80) == 0 ? gif_states.gif_image_start : gif_states.gif_global_colormap;
break;
case gif_states.gif_global_colormap:
var ct = new ColorTable(colorTableSize);
for (int i = 0; i < colorTableSize; i++)
{
ct.AddItem(buf[p++]); //red
ct.AddItem(buf[p++]); //green
ct.AddItem(buf[p++]); //blue
}
ColorSpace.AddColorTable(ct);
state = gif_states.gif_image_start;
break;
case gif_states.gif_image_start:
int first_code = buf[p++];
if (first_code == 0x3b) //terminator ';'
{
state = gif_states.gif_done;
break;
}
if (first_code == 0x21) //extension '!'
{
state = gif_states.gif_extension;
break;
}
if (first_code != 0x2c) //invalid format , should be ','
throw new ImageFormatException("Invalid GIF format : image separator code (0x2C) not found.");
state = gif_states.gif_image_header;
break;
case gif_states.gif_extension:
int ext_code = buf[p++];
int jump_len = buf[p++];
state = gif_states.gif_skip_block;
switch (ext_code)
{
case 0xf9:
state = gif_states.gif_control_extension;
break;
case 0x01:
//just ignoring plain text extension
break;
case 0xff:
state = gif_states.gif_application_extension;
break;
case 0xfe:
state = gif_states.gif_consume_comment;
break;
}
if (jump_len > 0)
{
p = p + jump_len;
}
else
state = gif_states.gif_image_start;
break;
case gif_states.gif_consume_block:
if (buf[p] == 0)
{
state = gif_states.gif_image_start;
p++;
}
else
{
p = p + buf[p];
state = gif_states.gif_skip_block;
}
break;
case gif_states.gif_skip_block:
state = gif_states.gif_image_start;
break;
case gif_states.gif_control_extension:
// here i should check for transparency
state = gif_states.gif_consume_block;
break;
case gif_states.gif_comment_extension:
if (buf[p] > 0)
{
p = p + buf[p];
state = gif_states.gif_consume_comment;
}
else
state = gif_states.gif_image_start;
break;
case gif_states.gif_consume_comment:
state = gif_states.gif_comment_extension;
break;
case gif_states.gif_application_extension:
state = gif_states.gif_consume_block;
break;
case gif_states.gif_image_header:
p = p + 8;
packed_field = buf[p++];
int localColorTableFlag = (packed_field & 0x80); //bit 1
int interlaceFlag = (packed_field & 0x40); //bit 2
int sizeLocalColorTable = 2 << (packed_field & 0x07); //last 3 bits
if (localColorTableFlag > 0)
{
throw new ImageFormatException("Invalid GIF format : Local Color Tables not supported.");
}
if (interlaceFlag > 0)
{
throw new ImageFormatException("Invalid GIF format : Interlaced GIF's not supported.");
}
//i'm assuming there's no local color table
state = gif_states.gif_lzw_start;
break;
case gif_states.gif_lzw_start:
p++;
state = gif_states.gif_sub_block;
break;
case gif_states.gif_sub_block:
if (buf[p] != 0)
{
//read ahead
proc_sblock(buf, buf[p], p + 1);
ms.Flush();
m_bitmaps = ms.ToArray();
return;
}
break;
case gif_states.gif_done:
return;
}
}
}
