commit 6be5ab5f797e71adea62b6aec71b9bad343b7cf0
parent cb025bcd4e24edd37e5bb7687c15c9576a3fde9c
Author: Jack Mordaunt <jackmordaunt.dev@gmail.com>
Date: Sat, 29 Jan 2022 17:35:34 +0800
webp: bifurcate encoding and decoding logic
Signed-off-by: Jack Mordaunt <jackmordaunt.dev@gmail.com>
Diffstat:
| A | webp/decode.go | | | 16 | ++++++++++++++++ |
| A | webp/encode.go | | | 105 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| M | webp/webp.go | | | 109 | ------------------------------------------------------------------------------- |
3 files changed, 121 insertions(+), 109 deletions(-)
diff --git a/webp/decode.go b/webp/decode.go
@@ -0,0 +1,16 @@
+package webp
+
+import (
+ "fmt"
+ "image"
+ "io"
+)
+
+// Decode a webp into an image.
+func Decode(r io.Reader) (image.Image, error) {
+ return nil, fmt.Errorf("unimplemented")
+}
+
+func DecodeConfig(r io.Reader) (image.Config, error) {
+ return image.Config{}, fmt.Errorf("unimplemented")
+}
diff --git a/webp/encode.go b/webp/encode.go
@@ -0,0 +1,105 @@
+package webp
+
+import (
+ "fmt"
+ "image"
+ "io"
+ "runtime"
+ "unsafe"
+
+ "git.sr.ht/~jackmordaunt/go-libwebp/lib"
+ "modernc.org/libc"
+)
+
+// Encode an image into webp with default settings.
+func Encode(w io.Writer, m image.Image, opt ...EncodeOption) error {
+ var enc Encoder
+ for _, op := range opt {
+ op(&enc)
+ }
+ return enc.Encode(w, m)
+}
+
+// EncodeOption configures the encoder.
+type EncodeOption func(*Encoder)
+
+// Quality in the range (0,1].
+func Quality(q float32) EncodeOption {
+ return func(enc *Encoder) {
+ enc.Quality = q
+ }
+}
+
+// Lossless will ignore quality.
+func Lossless() EncodeOption {
+ return func(enc *Encoder) {
+ enc.Lossless = true
+ }
+}
+
+// Encoder implements webp encoding of an image.
+type Encoder struct {
+ // Quality is in the range (0,1]. Values outside of this
+ // range will be treated as 1.
+ Quality float32
+ // Lossless indicates whether to use the lossless compression
+ // strategy. If true, the Quality field is ignored.
+ Lossless bool
+}
+
+// Encode specified image as webp to w.
+func (enc *Encoder) Encode(w io.Writer, m image.Image) error {
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+ if enc.Quality <= 0.0 || enc.Quality > 1 {
+ enc.Quality = 1.0
+ }
+ rgbaImage := image.NewRGBA(m.Bounds())
+ rect := m.Bounds()
+ for y := rect.Min.Y; y < rect.Max.Y; y++ {
+ for x := rect.Min.X; x < rect.Max.X; x++ {
+ rgbaImage.Set(x, y, m.At(x, y))
+ }
+ }
+ var (
+ // out buffer to contain webp data.
+ out *byte = nil
+ )
+ size := lib.Encode(
+ libc.NewTLS(),
+ uintptr(unsafe.Pointer(&rgbaImage.Pix[0])),
+ int32(rect.Dx()),
+ int32(rect.Dy()),
+ int32(rgbaImage.Stride),
+ // Function pointers are generated by taking a pointer to
+ // a struct who's first field is that function.
+ *(*uintptr)(unsafe.Pointer(
+ &struct {
+ f func(tls *libc.TLS, picture uintptr, rgba uintptr, rgba_stride int32) int32
+ }{
+ lib.WebPPictureImportRGBA,
+ },
+ )),
+ // quality for libwebp is [0,100].
+ float32(enc.Quality*100),
+ boolToInt32(enc.Lossless),
+ uintptr(unsafe.Pointer(&out)),
+ )
+ if size == 0 {
+ return fmt.Errorf("encoding webp image: size %d", size)
+ }
+ if out == nil {
+ return fmt.Errorf("failed to allocate memory; probably errored")
+ }
+ if _, err := w.Write(libc.GoBytes(uintptr(unsafe.Pointer(out)), int(size))); err != nil {
+ return fmt.Errorf("writing webp data: %w", err)
+ }
+ return nil
+}
+
+func boolToInt32(b bool) int32 {
+ if b {
+ return 1
+ }
+ return 0
+}
diff --git a/webp/webp.go b/webp/webp.go
@@ -2,118 +2,9 @@
package webp
import (
- "fmt"
"image"
- "io"
- "runtime"
- "unsafe"
-
- "git.sr.ht/~jackmordaunt/go-libwebp/lib"
- "modernc.org/libc"
)
func init() {
image.RegisterFormat("webp", "RIFF????WEBP", Decode, DecodeConfig)
}
-
-// EncodeOption configures the encoder.
-type EncodeOption func(*Encoder)
-
-// Quality in the range (0,1].
-func Quality(q float32) EncodeOption {
- return func(enc *Encoder) {
- enc.Quality = q
- }
-}
-
-// Lossless will ignore quality.
-func Lossless() EncodeOption {
- return func(enc *Encoder) {
- enc.Lossless = true
- }
-}
-
-// Encode an image into webp with default settings.
-func Encode(w io.Writer, m image.Image, opt ...EncodeOption) error {
- var enc Encoder
- for _, op := range opt {
- op(&enc)
- }
- return enc.Encode(w, m)
-}
-
-// Decode a webp into an image.
-func Decode(r io.Reader) (image.Image, error) {
- return nil, fmt.Errorf("unimplemented")
-}
-
-func DecodeConfig(r io.Reader) (image.Config, error) {
- return image.Config{}, fmt.Errorf("unimplemented")
-}
-
-// Encoder implements webp encoding of an image.
-type Encoder struct {
- // Quality is in the range (0,1]. Values outside of this
- // range will be treated as 1.
- Quality float32
- // Lossless indicates whether to use the lossless compression
- // strategy. If true, the Quality field is ignored.
- Lossless bool
-}
-
-// Encode specified image as webp to w.
-func (enc *Encoder) Encode(w io.Writer, m image.Image) error {
- runtime.LockOSThread()
- defer runtime.UnlockOSThread()
- if enc.Quality <= 0.0 || enc.Quality > 1 {
- enc.Quality = 1.0
- }
- rgbaImage := image.NewRGBA(m.Bounds())
- rect := m.Bounds()
- for y := rect.Min.Y; y < rect.Max.Y; y++ {
- for x := rect.Min.X; x < rect.Max.X; x++ {
- rgbaImage.Set(x, y, m.At(x, y))
- }
- }
- var (
- // out buffer to contain webp data.
- out *byte = nil
- )
- size := lib.Encode(
- libc.NewTLS(),
- uintptr(unsafe.Pointer(&rgbaImage.Pix[0])),
- int32(rect.Dx()),
- int32(rect.Dy()),
- int32(rgbaImage.Stride),
- // Function pointers are generated by taking a pointer to
- // a struct who's first field is that function.
- *(*uintptr)(unsafe.Pointer(
- &struct {
- f func(tls *libc.TLS, picture uintptr, rgba uintptr, rgba_stride int32) int32
- }{
- lib.WebPPictureImportRGBA,
- },
- )),
- // quality for libwebp is [0,100].
- float32(enc.Quality*100),
- boolToInt32(enc.Lossless),
- uintptr(unsafe.Pointer(&out)),
- )
- if size == 0 {
- return fmt.Errorf("encoding webp image: size %d", size)
- }
- if out == nil {
- return fmt.Errorf("failed to allocate memory; probably errored")
- }
- if _, err := w.Write(libc.GoBytes(uintptr(unsafe.Pointer(out)), int(size))); err != nil {
- return fmt.Errorf("writing webp data: %w", err)
- }
- return nil
-}
-
-func boolToInt32(b bool) int32 {
- if b {
- return 1
- }
- return 0
-}
