/
ico.go
214 lines (182 loc) · 4.97 KB
/
ico.go
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// Package ico describes Windows ICO file format.
package ico
// ICO: http://msdn.microsoft.com/en-us/library/ms997538.aspx
// BMP/DIB: http://msdn.microsoft.com/en-us/library/windows/desktop/dd183562%28v=vs.85%29.aspx
import (
"bytes"
"encoding/binary"
"fmt"
"image"
"image/color"
"io"
"io/ioutil"
"sort"
)
const (
BI_RGB = 0
)
type ICONDIR struct {
Reserved uint16 // must be 0
Type uint16 // Resource Type (1 for icons)
Count uint16 // How many images?
}
type IconDirEntryCommon struct {
Width byte // Width, in pixels, of the image
Height byte // Height, in pixels, of the image
ColorCount byte // Number of colors in image (0 if >=8bpp)
Reserved byte // Reserved (must be 0)
Planes uint16 // Color Planes
BitCount uint16 // Bits per pixel
BytesInRes uint32 // How many bytes in this resource?
}
type ICONDIRENTRY struct {
IconDirEntryCommon
ImageOffset uint32 // Where in the file is this image? [from beginning of file]
}
type BITMAPINFOHEADER struct {
Size uint32
Width int32
Height int32 // NOTE: "represents the combined height of the XOR and AND masks. Remember to divide this number by two before using it to perform calculations for either of the XOR or AND masks."
Planes uint16 // [BMP/DIB]: "is always 1"
BitCount uint16
Compression uint32 // for ico = 0
SizeImage uint32
XPelsPerMeter int32 // for ico = 0
YPelsPerMeter int32 // for ico = 0
ClrUsed uint32 // for ico = 0
ClrImportant uint32 // for ico = 0
}
type RGBQUAD struct {
Blue byte
Green byte
Red byte
Reserved byte // must be 0
}
func skip(r io.Reader, n int64) error {
_, err := io.CopyN(ioutil.Discard, r, n)
return err
}
type icoOffset struct {
n int
offset uint32
}
type rawico struct {
icoinfo ICONDIRENTRY
bmpinfo *BITMAPINFOHEADER
idx int
data []byte
}
type byOffsets []rawico
func (o byOffsets) Len() int { return len(o) }
func (o byOffsets) Less(i, j int) bool { return o[i].icoinfo.ImageOffset < o[j].icoinfo.ImageOffset }
func (o byOffsets) Swap(i, j int) {
tmp := o[i]
o[i] = o[j]
o[j] = tmp
}
type ICO struct {
image.Image
}
func DecodeHeaders(r io.Reader) ([]ICONDIRENTRY, error) {
var hdr ICONDIR
err := binary.Read(r, binary.LittleEndian, &hdr)
if err != nil {
return nil, err
}
if hdr.Reserved != 0 || hdr.Type != 1 {
return nil, fmt.Errorf("bad magic number")
}
entries := make([]ICONDIRENTRY, hdr.Count)
for i := 0; i < len(entries); i++ {
err = binary.Read(r, binary.LittleEndian, &entries[i])
if err != nil {
return nil, err
}
}
return entries, nil
}
// NOTE: won't succeed on files with overlapping offsets
func unused_decodeAll(r io.Reader) ([]*ICO, error) {
var hdr ICONDIR
err := binary.Read(r, binary.LittleEndian, &hdr)
if err != nil {
return nil, err
}
if hdr.Reserved != 0 || hdr.Type != 1 {
return nil, fmt.Errorf("bad magic number")
}
raws := make([]rawico, hdr.Count)
for i := 0; i < len(raws); i++ {
err = binary.Read(r, binary.LittleEndian, &raws[i].icoinfo)
if err != nil {
return nil, err
}
raws[i].idx = i
}
sort.Sort(byOffsets(raws))
offset := uint32(binary.Size(&hdr) + len(raws)*binary.Size(ICONDIRENTRY{}))
for i := 0; i < len(raws); i++ {
err = skip(r, int64(raws[i].icoinfo.ImageOffset-offset))
if err != nil {
return nil, err
}
offset = raws[i].icoinfo.ImageOffset
raws[i].bmpinfo = &BITMAPINFOHEADER{}
err = binary.Read(r, binary.LittleEndian, raws[i].bmpinfo)
if err != nil {
return nil, err
}
err = skip(r, int64(raws[i].bmpinfo.Size-uint32(binary.Size(BITMAPINFOHEADER{}))))
if err != nil {
return nil, err
}
raws[i].data = make([]byte, raws[i].icoinfo.BytesInRes-raws[i].bmpinfo.Size)
_, err = io.ReadFull(r, raws[i].data)
if err != nil {
return nil, err
}
}
icos := make([]*ICO, len(raws))
for i := 0; i < len(raws); i++ {
fmt.Println(i)
icos[raws[i].idx], err = decode(raws[i].bmpinfo, &raws[i].icoinfo, raws[i].data)
if err != nil {
return nil, err
}
}
return icos, nil
}
func decode(info *BITMAPINFOHEADER, icoinfo *ICONDIRENTRY, data []byte) (*ICO, error) {
if info.Compression != BI_RGB {
return nil, fmt.Errorf("ICO compression not supported (got %d)", info.Compression)
}
//if info.ClrUsed!=0 {
// panic(info.ClrUsed)
//}
r := bytes.NewBuffer(data)
bottomup := info.Height > 0
if !bottomup {
info.Height = -info.Height
}
switch info.BitCount {
case 8:
ncol := int(icoinfo.ColorCount)
if ncol == 0 {
ncol = 256
}
pal := make(color.Palette, ncol)
for i := 0; i < ncol; i++ {
var rgb RGBQUAD
err := binary.Read(r, binary.LittleEndian, &rgb)
if err != nil {
return nil, err
}
pal[i] = color.NRGBA{R: rgb.Red, G: rgb.Green, B: rgb.Blue, A: 0xff} //FIXME: is Alpha ok 0xff?
}
fmt.Println(pal)
fmt.Println(info.SizeImage, len(data)-binary.Size(RGBQUAD{})*len(pal), info.Width, info.Height)
default:
return nil, fmt.Errorf("unsupported ICO bit depth (BitCount) %d", info.BitCount)
}
return nil, nil
}