diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/image/gif/reader.go | 41 |
1 files changed, 34 insertions, 7 deletions
diff --git a/src/image/gif/reader.go b/src/image/gif/reader.go index 5a863e204f..b3ed0388f4 100644 --- a/src/image/gif/reader.go +++ b/src/image/gif/reader.go @@ -34,6 +34,9 @@ const ( // Fields. fColorMapFollows = 1 << 7 + // Screen Descriptor flags. + sdGlobalColorTable = 1 << 7 + // Image fields. ifLocalColorTable = 1 << 7 ifInterlace = 1 << 6 @@ -41,6 +44,14 @@ const ( // Graphic control flags. gcTransparentColorSet = 1 << 0 + gcDisposalMethodMask = 7 << 2 +) + +// Disposal Methods. +const ( + DisposalNone = 0x01 + DisposalBackground = 0x02 + DisposalPrevious = 0x03 ) // Section indicators. @@ -66,11 +77,11 @@ type decoder struct { vers string width int height int - flags byte headerFields byte backgroundIndex byte loopCount int delayTime int + disposalMethod byte // Unused from header. aspect byte @@ -87,9 +98,10 @@ type decoder struct { globalColorMap color.Palette // Used when decoding. - delay []int - image []*image.Paletted - tmp [1024]byte // must be at least 768 so we can read color map + delay []int + disposal []byte + image []*image.Paletted + tmp [1024]byte // must be at least 768 so we can read color map } // blockReader parses the block structure of GIF image data, which @@ -235,6 +247,7 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error { d.image = append(d.image, m) d.delay = append(d.delay, d.delayTime) + d.disposal = append(d.disposal, d.disposalMethod) // The GIF89a spec, Section 23 (Graphic Control Extension) says: // "The scope of this extension is the first graphic rendering block // to follow." We therefore reset the GCE fields to zero. @@ -265,7 +278,9 @@ func (d *decoder) readHeaderAndScreenDescriptor() error { d.width = int(d.tmp[6]) + int(d.tmp[7])<<8 d.height = int(d.tmp[8]) + int(d.tmp[9])<<8 d.headerFields = d.tmp[10] - d.backgroundIndex = d.tmp[11] + if d.headerFields&sdGlobalColorTable != 0 { + d.backgroundIndex = d.tmp[11] + } d.aspect = d.tmp[12] d.loopCount = -1 d.pixelSize = uint(d.headerFields&7) + 1 @@ -346,9 +361,10 @@ func (d *decoder) readGraphicControl() error { if _, err := io.ReadFull(d.r, d.tmp[0:6]); err != nil { return fmt.Errorf("gif: can't read graphic control: %s", err) } - d.flags = d.tmp[1] + flags := d.tmp[1] + d.disposalMethod = (flags & gcDisposalMethodMask) >> 2 d.delayTime = int(d.tmp[2]) | int(d.tmp[3])<<8 - if d.flags&gcTransparentColorSet != 0 { + if flags&gcTransparentColorSet != 0 { d.transparentIndex = d.tmp[4] d.hasTransparentIndex = true } @@ -428,7 +444,11 @@ func Decode(r io.Reader) (image.Image, error) { type GIF struct { Image []*image.Paletted // The successive images. Delay []int // The successive delay times, one per frame, in 100ths of a second. + Disposal []byte // The successive disposal methods, one per frame. LoopCount int // The loop count. + Config image.Config + // The background index in the Global Color Map. + BackgroundIndex byte } // DecodeAll reads a GIF image from r and returns the sequential frames @@ -442,6 +462,13 @@ func DecodeAll(r io.Reader) (*GIF, error) { Image: d.image, LoopCount: d.loopCount, Delay: d.delay, + Disposal: d.disposal, + Config: image.Config{ + ColorModel: d.globalColorMap, + Width: d.width, + Height: d.height, + }, + BackgroundIndex: d.backgroundIndex, } return gif, nil } |