func vipsShrinkJpeg(buf []byte, input *C.VipsImage, shrink int) (*C.VipsImage, error) {
var image *C.VipsImage
defer C.g_object_unref(C.gpointer(input))
err := C.vips_jpegload_buffer_shrink(unsafe.Pointer(&buf[0]), C.size_t(len(buf)), &image, C.int(shrink))
if err != 0 {
return nil, catchVipsError()
}
return image, nil
}
func Resize(buf []byte, o Options) ([]byte, error) {
debug("%#+v", o)
// detect (if possible) the file type
typ := UNKNOWN
switch {
case bytes.Equal(buf[:2], MARKER_JPEG):
typ = JPEG
case bytes.Equal(buf[:2], MARKER_PNG):
typ = PNG
default:
return nil, errors.New("unknown image format")
}
// create an image instance
var image, tmpImage *C.struct__VipsImage
// feed it
switch typ {
case JPEG:
C.vips_jpegload_buffer_seq(unsafe.Pointer(&buf[0]), C.size_t(len(buf)), &image)
case PNG:
C.vips_pngload_buffer_seq(unsafe.Pointer(&buf[0]), C.size_t(len(buf)), &image)
}
// cleanup
defer func() {
C.vips_thread_shutdown()
C.vips_error_clear()
}()
// defaults
if o.Quality == 0 {
o.Quality = 100
}
// get WxH
inWidth := int(image.Xsize)
inHeight := int(image.Ysize)
// prepare for factor
factor := 0.0
// image calculations
switch {
// Fixed width and height
case o.Width > 0 && o.Height > 0:
xf := float64(inWidth) / float64(o.Width)
yf := float64(inHeight) / float64(o.Height)
if o.Crop {
factor = math.Min(xf, yf)
} else {
factor = math.Max(xf, yf)
}
// Fixed width, auto height
case o.Width > 0:
factor = float64(inWidth) / float64(o.Width)
o.Height = int(math.Floor(float64(inHeight) / factor))
// Fixed height, auto width
case o.Height > 0:
factor = float64(inHeight) / float64(o.Height)
o.Width = int(math.Floor(float64(inWidth) / factor))
// Identity transform
default:
factor = 1
o.Width = inWidth
o.Height = inHeight
}
debug("transform from %dx%d to %dx%d", inWidth, inHeight, o.Width, o.Height)
// shrink
shrink := int(math.Floor(factor))
if shrink < 1 {
shrink = 1
}
// residual
residual := float64(shrink) / factor
// Do not enlarge the output if the input width *or* height are already less than the required dimensions
if !o.Enlarge {
if inWidth < o.Width && inHeight < o.Height {
factor = 1
shrink = 1
residual = 0
o.Width = inWidth
o.Height = inHeight
}
}
debug("factor: %v, shrink: %v, residual: %v", factor, shrink, residual)
// Try to use libjpeg shrink-on-load
shrinkOnLoad := 1
if typ == JPEG && shrink >= 2 {
switch {
case shrink >= 8:
factor = factor / 8
shrinkOnLoad = 8
case shrink >= 4:
factor = factor / 4
shrinkOnLoad = 4
case shrink >= 2:
factor = factor / 2
shrinkOnLoad = 2
}
}
if shrinkOnLoad > 1 {
debug("shrink on load %d", shrinkOnLoad)
// Recalculate integral shrink and double residual
factor = math.Max(factor, 1.0)
shrink = int(math.Floor(factor))
residual = float64(shrink) / factor
// Reload input using shrink-on-load
err := C.vips_jpegload_buffer_shrink(unsafe.Pointer(&buf[0]), C.size_t(len(buf)), &tmpImage, C.int(shrinkOnLoad))
C.g_object_unref(C.gpointer(image))
image = tmpImage
if err != 0 {
return nil, resizeError()
}
}
if shrink > 1 {
debug("shrink %d", shrink)
// Use vips_shrink with the integral reduction
err := C.vips_shrink_0(image, &tmpImage, C.double(float64(shrink)), C.double(float64(shrink)))
C.g_object_unref(C.gpointer(image))
image = tmpImage
if err != 0 {
return nil, resizeError()
}
// Recalculate residual float based on dimensions of required vs shrunk images
shrunkWidth := int(image.Xsize)
shrunkHeight := int(image.Ysize)
residualx := float64(o.Width) / float64(shrunkWidth)
residualy := float64(o.Height) / float64(shrunkHeight)
if o.Crop {
residual = math.Max(residualx, residualy)
} else {
residual = math.Min(residualx, residualy)
}
}
// Use vips_affine with the remaining float part
debug("residual: %v", residual)
if residual != 0 {
debug("residual %.2f", residual)
// Create interpolator - "bilinear" (default), "bicubic" or "nohalo"
is := C.CString(o.Interpolator.String())
interpolator := C.vips_interpolate_new(is)
// Perform affine transformation
err := C.vips_affine_interpolator(image, &tmpImage, C.double(residual), 0, 0, C.double(residual), interpolator)
C.g_object_unref(C.gpointer(image))
image = tmpImage
C.free(unsafe.Pointer(is))
C.g_object_unref(C.gpointer(interpolator))
if err != 0 {
return nil, resizeError()
}
}
// Crop/embed
affinedWidth := int(image.Xsize)
affinedHeight := int(image.Ysize)
if affinedWidth != o.Width || affinedHeight != o.Height {
if o.Crop {
// Crop
debug("cropping")
left, top := sharpCalcCrop(affinedWidth, affinedHeight, o.Width, o.Height, o.Gravity)
o.Width = int(math.Min(float64(affinedWidth), float64(o.Width)))
o.Height = int(math.Min(float64(affinedHeight), float64(o.Height)))
err := C.vips_extract_area_0(image, &tmpImage, C.int(left), C.int(top), C.int(o.Width), C.int(o.Height))
C.g_object_unref(C.gpointer(image))
image = tmpImage
if err != 0 {
return nil, resizeError()
}
} else if o.Embed {
debug("embedding with extend %d", o.Extend)
left := (o.Width - affinedWidth) / 2
top := (o.Height - affinedHeight) / 2
err := C.vips_embed_extend(image, &tmpImage, C.int(left), C.int(top), C.int(o.Width), C.int(o.Height), C.int(o.Extend))
C.g_object_unref(C.gpointer(image))
image = tmpImage
if err != 0 {
return nil, resizeError()
}
}
} else {
debug("canvased same as affined")
}
// Always convert to sRGB colour space
C.vips_colourspace_0(image, &tmpImage, C.VIPS_INTERPRETATION_sRGB)
C.g_object_unref(C.gpointer(image))
image = tmpImage
// Finally save
length := C.size_t(0)
var ptr unsafe.Pointer
C.vips_jpegsave_custom(image, &ptr, &length, 1, C.int(o.Quality), 0)
C.g_object_unref(C.gpointer(image))
// get back the buffer
buf = C.GoBytes(ptr, C.int(length))
C.g_free(C.gpointer(ptr))
return buf, nil
}