Add support for read and create hdf5 true color image dataset

h5g_group.go

@@ -11,7 +11,9 @@ package hdf5
 import "C"
 
 import (
+	"errors"
 	"fmt"
+	"image"
 	"unsafe"
 )
 
@@ -169,3 +171,19 @@ func (g *CommonFG) LinkExists(name string) bool {
 	defer C.free(unsafe.Pointer(c_name))
 	return C.H5Lexists(g.id, c_name, 0) > 0
 }
+
+// CreateImage create a image(RGB only) set with given name in the receiver.
+func (g *CommonFG) CreateImage(name string, img image.Image) error {
+	if g.LinkExists(name) {
+		return errors.New("hdf5: name already exist")
+	}
+	return newImage(g.id, name, img)
+}
+
+// ReadImage read a image dataset, returning it as an image.Image.
+func (g *CommonFG) ReadImage(name string) (image.Image, error) {
+	if !g.LinkExists(name) {
+		return nil, errors.New("hdf5: name doesn't exist")
+	}
+	return getImage(g.id, name)
+}

h5g_group_test.go

@@ -5,6 +5,9 @@
 package hdf5
 
 import (
+	"image"
+	"image/color"
+	"image/jpeg"
 	"os"
 	"testing"
 )
@@ -128,3 +131,51 @@ func TestGroup(t *testing.T) {
 	}
 
 }
+
+func TestImage(t *testing.T) {
+	f, err := CreateFile(fname, F_ACC_TRUNC)
+	if err != nil {
+		t.Fatalf("CreateFile failed: %v", err)
+	}
+	defer os.Remove(fname)
+	defer f.Close()
+	img := image.NewRGBA(image.Rect(0, 0, 1000, 500))
+	for y := 200; y < 300; y++ {
+		for x := 400; x < 600; x++ {
+			img.Set(x, y, color.RGBA{255, 0, 255, 255})
+		}
+	}
+	if err != nil {
+		t.Fatalf("image decoding failed: %v", err)
+	}
+	g1, err := f.CreateGroup("foo")
+	if err != nil {
+		t.Fatalf("couldn't create group: %v", err)
+	}
+	defer g1.Close()
+	err = g1.CreateImage("image", img)
+	if err != nil {
+		t.Fatalf("image saving failed: %v", err)
+	}
+	imgRead, err := g1.ReadImage("image")
+	if err != nil {
+		t.Fatalf("image reading failed: %v", err)
+	}
+	gotWidth := imgRead.Bounds().Max.X
+	gotHeight := imgRead.Bounds().Max.Y
+	if gotWidth != 1000 || gotHeight != 500 {
+		t.Errorf("image dimension mismatch: got %dx%d, want:1000x500", gotWidth, gotHeight)
+	}
+
+	imgfile, err := os.Create("img.jpg")
+	if err != nil {
+		t.Fatalf("image file creation failed: %v", err)
+	}
+	defer os.Remove("img.jpg")
+	defer imgfile.Close()
+
+	err = jpeg.Encode(imgfile, imgRead, nil)
+	if err != nil {
+		t.Errorf("unexpected error saving image: %v", err)
+	}
+}

h5i_image.go

@@ -0,0 +1,74 @@
+// license that can be found in the LICENSE file.
+
+package hdf5
+
+// #include "hdf5.h"
+// #include "hdf5_hl.h"
+// #include <stdlib.h>
+// #include <string.h>
+import "C"
+
+import (
+	"errors"
+	"image"
+	"image/color"
+	"unsafe"
+)
+
+// newImage takes a image object and convert it to a hdf5 format and write to the id node
+func newImage(id C.hid_t, name string, img image.Image) error {
+	width := img.Bounds().Max.X
+	height := img.Bounds().Max.Y
+	var c_width, c_height C.hsize_t
+	c_name := C.CString(name)
+	defer C.free(unsafe.Pointer(c_name))
+	var buf []byte
+	for y := 0; y < height; y++ {
+		for x := 0; x < width; x++ {
+			r, g, b, _ := img.At(x, y).RGBA()
+			buf = append(buf, byte(r>>8), byte(g>>8), byte(b>>8))
+		}
+	}
+	c_width = C.hsize_t(width)
+	c_height = C.hsize_t(height)
+	c_image := (*C.uchar)(unsafe.Pointer(&buf[0]))
+
+	status := C.H5IMmake_image_24bit(id, c_name, c_width, c_height, C.CString("INTERLACE_PIXEL"), c_image)
+	if status < 0 {
+		return errors.New("hdf5: failed to create true color image")
+	}
+	return nil
+}
+
+//
+func getImage(id C.hid_t, name string) (image.Image, error) {
+	//TODO(zyc-sudo) Should handle interlace and npal better, yet these two are not needed for simple image read and write.
+	var width, height, planes C.hsize_t
+	var npals C.hssize_t
+	var interlace C.char
+	c_name := C.CString(name)
+	defer C.free(unsafe.Pointer(c_name))
+	rc := C.H5IMget_image_info(id, c_name, &width, &height, &planes, &interlace, &npals)
+	err := h5err(rc)
+	if err != nil {
+		return nil, err
+	}
+	gbuf := make([]uint8, width*height*planes)
+	c_image := (*C.uchar)(unsafe.Pointer(&gbuf[0]))
+	rc = C.H5IMread_image(id, c_name, c_image)
+
+	err = h5err(rc)
+	if err != nil {
+		return nil, err
+	}
+
+	g_width := int(width)
+	g_height := int(height)
+	img := image.NewRGBA(image.Rect(0, 0, g_width, g_height))
+	for y := 0; y < g_height; y++ {
+		for x := 0; x < g_width; x++ {
+			img.Set(x, y, color.RGBA{gbuf[y*g_width*3+x*3], gbuf[y*g_width*3+x*3+1], gbuf[y*g_width*3+x*3+2], 255})
+		}
+	}
+	return img, err
+}