idiomatic error handling, bind more functions

imagequant.go

@@ -12,19 +12,39 @@ import (
 */
 import "C"
 
-type ImageQuantErr int
-
 var (
-	ErrOK                 = ImageQuantErr(C.LIQ_OK)
-	ErrQualityTooLow      = ImageQuantErr(C.LIQ_QUALITY_TOO_LOW)
-	ErrValueOutOfRange    = ImageQuantErr(C.LIQ_VALUE_OUT_OF_RANGE)
-	ErrOutOfMemory        = ImageQuantErr(C.LIQ_OUT_OF_MEMORY)
-	ErrAborted            = ImageQuantErr(C.LIQ_ABORTED)
-	ErrBitmapNotAvailable = ImageQuantErr(C.LIQ_BITMAP_NOT_AVAILABLE)
-	ErrBufferTooSmall     = ImageQuantErr(C.LIQ_BUFFER_TOO_SMALL)
-	ErrInvalidPointer     = ImageQuantErr(C.LIQ_INVALID_POINTER)
+	ErrQualityTooLow      = errors.New("Quality too low")
+	ErrValueOutOfRange    = errors.New("Value out of range")
+	ErrOutOfMemory        = errors.New("Out of memory")
+	ErrAborted            = errors.New("Aborted")
+	ErrBitmapNotAvailable = errors.New("Bitmap not available")
+	ErrBufferTooSmall     = errors.New("Buffer too small")
+	ErrInvalidPointer     = errors.New("Invalid pointer")
 )
 
+func translateError(iqe C.liq_error) error {
+	switch iqe {
+	case C.LIQ_OK:
+		return nil
+	case (C.LIQ_QUALITY_TOO_LOW):
+		return ErrQualityTooLow
+	case (C.LIQ_VALUE_OUT_OF_RANGE):
+		return ErrValueOutOfRange
+	case (C.LIQ_OUT_OF_MEMORY):
+		return ErrOutOfMemory
+	case (C.LIQ_ABORTED):
+		return ErrAborted
+	case (C.LIQ_BITMAP_NOT_AVAILABLE):
+		return ErrBitmapNotAvailable
+	case (C.LIQ_BUFFER_TOO_SMALL):
+		return ErrBufferTooSmall
+	case (C.LIQ_INVALID_POINTER):
+		return ErrInvalidPointer
+	default:
+		return errors.New("Unknown error")
+	}
+}
+
 func GetLibraryVersion() int {
 	return int(C.liq_version())
 }
@@ -43,18 +63,16 @@ func NewAttributes() (*Attributes, error) {
 	return &Attributes{p: pAttr}, nil
 }
 
-func (this *Attributes) SetMaxColors(colors int) ImageQuantErr {
-	ret := C.liq_set_max_colors(this.p, C.int(colors))
-	return ImageQuantErr(ret)
+func (this *Attributes) SetMaxColors(colors int) error {
+	return translateError(C.liq_set_max_colors(this.p, C.int(colors)))
 }
 
 func (this *Attributes) GetMaxColors() int {
 	return int(C.liq_get_max_colors(this.p))
 }
 
-func (this *Attributes) SetQuality(minimum, maximum int) ImageQuantErr {
-	ret := C.liq_set_quality(this.p, C.int(minimum), C.int(maximum))
-	return ImageQuantErr(ret)
+func (this *Attributes) SetQuality(minimum, maximum int) error {
+	return translateError(C.liq_set_quality(this.p, C.int(minimum), C.int(maximum)))
 }
 
 func (this *Attributes) GetMinQuality() int {
@@ -75,14 +93,41 @@ type Image struct {
 }
 
 // Callers MUST call Release() on the returned object to free memory.
-func NewImage(attr *Attributes, rgba32data string, width, height int, gamma float64) *Image {
+func NewImage(attr *Attributes, rgba32data string, width, height int, gamma float64) (*Image, error) {
 	pImg := C.liq_image_create_rgba(attr.p, unsafe.Pointer(C.CString(rgba32data)), C.int(width), C.int(height), C.double(gamma))
+	if pImg == nil {
+		return nil, errors.New("Failed to create image (invalid argument)")
+	}
+
 	return &Image{
 		p: pImg,
-	}
+	}, nil
 }
 
 // Free memory. Callers must not use this object after Release has been called.
 func (this *Image) Release() {
 	C.liq_image_destroy(this.p)
 }
+
+type Result struct {
+	p *C.struct_liq_result
+}
+
+func (this *Image) Quantize(attr *Attributes) (*Result, error) {
+	res := Result{}
+	liqerr := C.liq_image_quantize(this.p, attr.p, &res.p)
+	if liqerr != C.LIQ_OK {
+		return nil, translateError(liqerr)
+	}
+
+	return &res, nil
+}
+
+func (this *Result) SetDitheringLevel(dither_level float32) error {
+	return translateError(C.liq_set_dithering_level(this.p, C.float(dither_level)))
+}
+
+// Free memory. Callers must not use this object after Release has been called.
+func (this *Result) Release() {
+	C.liq_result_destroy(this.p)
+}