Add option to convert embedded ICC profiles

Set an bimg.Options OutputICC to an absolute path to the desired output ICC profile. If an embedded ICC profile is found in VipsImage, it is converted to the output ICC profile.
Fixes #50

options.go

@@ -215,4 +215,5 @@ type Options struct {
 	Interpretation Interpretation
 	GaussianBlur   GaussianBlur
 	Sharpen        Sharpen
+	OutputICC      string
 }

resize.go

@@ -161,6 +161,7 @@ func saveImage(image *C.VipsImage, o Options) ([]byte, error) {
 		Interlace:      o.Interlace,
 		NoProfile:      o.NoProfile,
 		Interpretation: o.Interpretation,
+		OutputICC:      o.OutputICC,
 	}
 	// Finally get the resultant buffer
 	return vipsSave(image, saveOptions)

vips.go

@@ -55,6 +55,7 @@ type vipsSaveOptions struct {
 	Type           ImageType
 	Interlace      bool
 	NoProfile      bool
+	OutputICC      string // Absolute path to the output ICC profile
 	Interpretation Interpretation
 }
 
@@ -362,6 +363,7 @@ func vipsFlattenBackground(image *C.VipsImage, background Color) (*C.VipsImage,
 }
 
 func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
+	var outImage *C.VipsImage
 	// Remove ICC profile metadata
 	if o.NoProfile {
 		C.remove_profile(image)
@@ -374,7 +376,6 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 	interpretation := C.VipsInterpretation(o.Interpretation)
 
 	// Apply the proper colour space
-	var outImage *C.VipsImage
 	if vipsColourspaceIsSupported(image) {
 		err := C.vips_colourspace_bridge(image, &outImage, interpretation)
 		if int(err) != 0 {
@@ -383,6 +384,18 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 		image = outImage
 	}
 
+	if o.OutputICC != "" && vipsHasProfile(image) {
+		debug("Embedded ICC profile found, trying to convert to %s", o.OutputICC)
+		outputIccPath := C.CString(o.OutputICC)
+		defer C.free(unsafe.Pointer(outputIccPath))
+
+		err := C.vips_icc_transform_bridge(image, &outImage, outputIccPath)
+		if int(err) != 0 {
+			return nil, catchVipsError()
+		}
+		image = outImage
+	}
+
 	return image, nil
 }
 

vips.h

@@ -260,6 +260,12 @@ vips_colourspace_bridge(VipsImage *in, VipsImage **out, VipsInterpretation space
 	return vips_colourspace(in, out, space, NULL);
 }
 
+int
+vips_icc_transform_bridge (VipsImage *in, VipsImage **out, const char *output_icc_profile) {
+	// `output_icc_profile` represents the absolute path to the output ICC profile file
+	return vips_icc_transform(in, out, output_icc_profile, "embedded", TRUE, NULL);
+}
+
 int
 vips_jpegsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int quality, int interlace) {
 	return vips_jpegsave_buffer(in, buf, len,