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path: root/vendor/golang.org/x/image/bmp/reader.go
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Diffstat (limited to 'vendor/golang.org/x/image/bmp/reader.go')
-rw-r--r--vendor/golang.org/x/image/bmp/reader.go199
1 files changed, 199 insertions, 0 deletions
diff --git a/vendor/golang.org/x/image/bmp/reader.go b/vendor/golang.org/x/image/bmp/reader.go
new file mode 100644
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+++ b/vendor/golang.org/x/image/bmp/reader.go
@@ -0,0 +1,199 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package bmp implements a BMP image decoder and encoder.
+//
+// The BMP specification is at http://www.digicamsoft.com/bmp/bmp.html.
+package bmp // import "golang.org/x/image/bmp"
+
+import (
+ "errors"
+ "image"
+ "image/color"
+ "io"
+)
+
+// ErrUnsupported means that the input BMP image uses a valid but unsupported
+// feature.
+var ErrUnsupported = errors.New("bmp: unsupported BMP image")
+
+func readUint16(b []byte) uint16 {
+ return uint16(b[0]) | uint16(b[1])<<8
+}
+
+func readUint32(b []byte) uint32 {
+ return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+}
+
+// decodePaletted reads an 8 bit-per-pixel BMP image from r.
+// If topDown is false, the image rows will be read bottom-up.
+func decodePaletted(r io.Reader, c image.Config, topDown bool) (image.Image, error) {
+ paletted := image.NewPaletted(image.Rect(0, 0, c.Width, c.Height), c.ColorModel.(color.Palette))
+ if c.Width == 0 || c.Height == 0 {
+ return paletted, nil
+ }
+ var tmp [4]byte
+ y0, y1, yDelta := c.Height-1, -1, -1
+ if topDown {
+ y0, y1, yDelta = 0, c.Height, +1
+ }
+ for y := y0; y != y1; y += yDelta {
+ p := paletted.Pix[y*paletted.Stride : y*paletted.Stride+c.Width]
+ if _, err := io.ReadFull(r, p); err != nil {
+ return nil, err
+ }
+ // Each row is 4-byte aligned.
+ if c.Width%4 != 0 {
+ _, err := io.ReadFull(r, tmp[:4-c.Width%4])
+ if err != nil {
+ return nil, err
+ }
+ }
+ }
+ return paletted, nil
+}
+
+// decodeRGB reads a 24 bit-per-pixel BMP image from r.
+// If topDown is false, the image rows will be read bottom-up.
+func decodeRGB(r io.Reader, c image.Config, topDown bool) (image.Image, error) {
+ rgba := image.NewRGBA(image.Rect(0, 0, c.Width, c.Height))
+ if c.Width == 0 || c.Height == 0 {
+ return rgba, nil
+ }
+ // There are 3 bytes per pixel, and each row is 4-byte aligned.
+ b := make([]byte, (3*c.Width+3)&^3)
+ y0, y1, yDelta := c.Height-1, -1, -1
+ if topDown {
+ y0, y1, yDelta = 0, c.Height, +1
+ }
+ for y := y0; y != y1; y += yDelta {
+ if _, err := io.ReadFull(r, b); err != nil {
+ return nil, err
+ }
+ p := rgba.Pix[y*rgba.Stride : y*rgba.Stride+c.Width*4]
+ for i, j := 0, 0; i < len(p); i, j = i+4, j+3 {
+ // BMP images are stored in BGR order rather than RGB order.
+ p[i+0] = b[j+2]
+ p[i+1] = b[j+1]
+ p[i+2] = b[j+0]
+ p[i+3] = 0xFF
+ }
+ }
+ return rgba, nil
+}
+
+// decodeNRGBA reads a 32 bit-per-pixel BMP image from r.
+// If topDown is false, the image rows will be read bottom-up.
+func decodeNRGBA(r io.Reader, c image.Config, topDown bool) (image.Image, error) {
+ rgba := image.NewNRGBA(image.Rect(0, 0, c.Width, c.Height))
+ if c.Width == 0 || c.Height == 0 {
+ return rgba, nil
+ }
+ y0, y1, yDelta := c.Height-1, -1, -1
+ if topDown {
+ y0, y1, yDelta = 0, c.Height, +1
+ }
+ for y := y0; y != y1; y += yDelta {
+ p := rgba.Pix[y*rgba.Stride : y*rgba.Stride+c.Width*4]
+ if _, err := io.ReadFull(r, p); err != nil {
+ return nil, err
+ }
+ for i := 0; i < len(p); i += 4 {
+ // BMP images are stored in BGRA order rather than RGBA order.
+ p[i+0], p[i+2] = p[i+2], p[i+0]
+ }
+ }
+ return rgba, nil
+}
+
+// Decode reads a BMP image from r and returns it as an image.Image.
+// Limitation: The file must be 8, 24 or 32 bits per pixel.
+func Decode(r io.Reader) (image.Image, error) {
+ c, bpp, topDown, err := decodeConfig(r)
+ if err != nil {
+ return nil, err
+ }
+ switch bpp {
+ case 8:
+ return decodePaletted(r, c, topDown)
+ case 24:
+ return decodeRGB(r, c, topDown)
+ case 32:
+ return decodeNRGBA(r, c, topDown)
+ }
+ panic("unreachable")
+}
+
+// DecodeConfig returns the color model and dimensions of a BMP image without
+// decoding the entire image.
+// Limitation: The file must be 8, 24 or 32 bits per pixel.
+func DecodeConfig(r io.Reader) (image.Config, error) {
+ config, _, _, err := decodeConfig(r)
+ return config, err
+}
+
+func decodeConfig(r io.Reader) (config image.Config, bitsPerPixel int, topDown bool, err error) {
+ // We only support those BMP images that are a BITMAPFILEHEADER
+ // immediately followed by a BITMAPINFOHEADER.
+ const (
+ fileHeaderLen = 14
+ infoHeaderLen = 40
+ )
+ var b [1024]byte
+ if _, err := io.ReadFull(r, b[:fileHeaderLen+infoHeaderLen]); err != nil {
+ return image.Config{}, 0, false, err
+ }
+ if string(b[:2]) != "BM" {
+ return image.Config{}, 0, false, errors.New("bmp: invalid format")
+ }
+ offset := readUint32(b[10:14])
+ if readUint32(b[14:18]) != infoHeaderLen {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ width := int(int32(readUint32(b[18:22])))
+ height := int(int32(readUint32(b[22:26])))
+ if height < 0 {
+ height, topDown = -height, true
+ }
+ if width < 0 || height < 0 {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ // We only support 1 plane, 8 or 24 bits per pixel and no compression.
+ planes, bpp, compression := readUint16(b[26:28]), readUint16(b[28:30]), readUint32(b[30:34])
+ if planes != 1 || compression != 0 {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ switch bpp {
+ case 8:
+ if offset != fileHeaderLen+infoHeaderLen+256*4 {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ _, err = io.ReadFull(r, b[:256*4])
+ if err != nil {
+ return image.Config{}, 0, false, err
+ }
+ pcm := make(color.Palette, 256)
+ for i := range pcm {
+ // BMP images are stored in BGR order rather than RGB order.
+ // Every 4th byte is padding.
+ pcm[i] = color.RGBA{b[4*i+2], b[4*i+1], b[4*i+0], 0xFF}
+ }
+ return image.Config{ColorModel: pcm, Width: width, Height: height}, 8, topDown, nil
+ case 24:
+ if offset != fileHeaderLen+infoHeaderLen {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ return image.Config{ColorModel: color.RGBAModel, Width: width, Height: height}, 24, topDown, nil
+ case 32:
+ if offset != fileHeaderLen+infoHeaderLen {
+ return image.Config{}, 0, false, ErrUnsupported
+ }
+ return image.Config{ColorModel: color.RGBAModel, Width: width, Height: height}, 32, topDown, nil
+ }
+ return image.Config{}, 0, false, ErrUnsupported
+}
+
+func init() {
+ image.RegisterFormat("bmp", "BM????\x00\x00\x00\x00", Decode, DecodeConfig)
+}