播放GIF时控制下一桢的显示

In Gif89a version,we can control the Render of the next frame,the format like this:
7 6 5 4 3 2 1 0 Field Name Type
+---------------+
0 | | Extension Introducer Byte
+---------------+
1 | | Graphic Control Label Byte
+---------------+

+---------------+
0 | | Block Size Byte
+---------------+
1 | | | | | <Packed Fields> See below
+---------------+
2 | | Delay Time Unsigned
+- -+
3 | |
+---------------+
4 | | Transparent Color Index Byte
+---------------+

+---------------+
0 | | Block Terminator Byte
+---------------+

=================================================================
<Packed Fields> = Reserved 3 Bits
Disposal Method 3 Bits
User Input Flag 1 Bit
Transparent Color Flag 1 Bit
=================================================================
Disposal Method - Indicates the way in which the graphic is to
be treated after being displayed.

Values : 0 - No disposal specified. The decoder is
not required to take any action.
1 - Do not dispose. The graphic is to be left
in place.
2 - Restore to background color. The area used by the
graphic must be restored to the background color.
3 - Restore to previous. The decoder is required to
restore the area overwritten by the graphic with
what was there prior to rendering the graphic.
4-7 - To be defined.
===================================

TFrameInfoFlags.iFlags =83 （TFrameInfoFlags.iFlags 转换为Tunit8）
For example 83=64|16|2|1, where | is the binary or operation. Practically addition in case of powers of 2.

Originally Posted by ImageData.h

EColor = 0x00000001, // this is the 1
ETransparencyPossible = 0x00000002, // this is the 2
ECanDither = 0x00000010, // this is the 16 (0x10)
ELeaveInPlace = 0x00000040, // and this is the 64 (0x40)
由此我们可以得到当绘制下一桢的时候是否需要保留前一帧的背景、颜色或者不保留等