https://github.com/jcbritobr/pnm
PNM is a collection of open image formats. This library supports ppm, pgm and pbm formats,
https://github.com/jcbritobr/pnm
decoder encoder go golang image image-processing pbm-image pgm-image pnm ppm-image
Last synced: about 2 months ago
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PNM is a collection of open image formats. This library supports ppm, pgm and pbm formats,
- Host: GitHub
- URL: https://github.com/jcbritobr/pnm
- Owner: jcbritobr
- License: mit
- Created: 2020-10-04T11:31:21.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2020-10-29T15:34:00.000Z (over 4 years ago)
- Last Synced: 2024-06-20T22:35:58.754Z (11 months ago)
- Topics: decoder, encoder, go, golang, image, image-processing, pbm-image, pgm-image, pnm, ppm-image
- Language: Go
- Homepage:
- Size: 868 KB
- Stars: 5
- Watchers: 2
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# PNM
PNM is a collection of open image formats. They are also referred as **portable anymap format(PNM)**. This library supports ppm(portable pixmap), pgm(portable graymap) and pbm(portable bitmap) formats. There is also an encoder and decoder implementations.
* Description \
Each file starts with a two byte magic number (in ascii) that identifies the type of the file it is (PPM, PGM, PBM) and its encoding (**ascii/plain or binary/raw**). The magic number is a capital P followed by a single-digit number. Below is a explanation table with **ascii/binary** magic number formats.
| **Type** | **Magic Number** | **Extension** | **Color** |
|-----------------|------------------|---------------|------------------------------------------------------------------------------|
| Portable Bitmap | P1/P4 | .pbm | 0-1(White & Black) |
| Portable GrayMap| P2/P5 | .pgm | 0-255(gray scale), variable, black to white range |
| Portable PixMap | P3/P6 | .ppm | 16 777 216 (0-255 for each RGB channel), some support for 0-65535 per channel|
The ascii/plain format allow for human readability and easy transfer to other platforms. The binary/raw formats are more efficient in size but will be dependent of platforms.
* Encoder usage
```go
import (
"math/rand"
"os"
"github.com/jcbritobr/pnm"
)
func main() {
image := pnm.NewPGMImage(800, 800, 255, pnm.PGMBinary)
file, err := os.Create("testdata/synimage.pgm")
if err != nil {
panic(err)
}
encoder := pnm.NewEncoder(file)
imgbuf := image.Buffer()
for i := range image.Buffer() {
data := rand.Intn(255-0) + 0
imgbuf[i] = byte(data)
}
err = encoder.Encode(image)
if err != nil {
panic(err)
}
}
```
* Decoder usage
```go
import (
"fmt"
"os"
"github.com/jcbritobr/pnm"
)
func main() {
var image pnm.PGMImage
file, err := os.Open("testdata/synimage.pgm")
if err != nil {
panic(err)
}
decoder := pnm.NewDecoder(file, pnm.PGMBinary)
err = decoder.Decode(&image)
if err != nil {
panic(err)
}
}
```
* Using ImageBuffer and color.Model (RGBA)
```go
import (
"os"
"github.com/jcbritobr/pnm"
"github.com/jcbritobr/pnm/buffer"
"github.com/jcbritobr/pnm/color"
)
func main() {
var image pnm.PPMImage
file, err := os.Open("testdata/tree_1.ppm")
if err != nil {
t.Errorf("fail with %v", err)
}
defer file.Close()
decoder := pnm.NewDecoder(file, pnm.PPMBinary)
err = decoder.Decode(&image)
if err != nil {
t.Errorf("fail to decode image %v", err)
}
imbuf := buffer.NewImageBuffer(image)
rgba := color.RGBA{}
newbuf := []byte{}
for {
n, _ := imbuf.Read(rgba[:])
if n <= 0 {
break
}
r, g, b, _ := rgba.RGBA()
r = 255 - r
g = 255 - g
b = 255 - b
newbuf = append(newbuf, r)
newbuf = append(newbuf, g)
newbuf = append(newbuf, b)
}
image.SetBuffer(newbuf)
fe, err := os.Create("testdata/tree_3.ppm")
if err != nil {
t.Errorf("fail to create file %v", err)
}
defer fe.Close()
encoder := pnm.NewEncoder(fe)
err = encoder.Encode(&image)
if err != nil {
t.Errorf("Encode() = %v want %v", err, nil)
}
}
```