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Add hasAlpha attribute to metadata API

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Provides internal sharp_image_has_alpha method

Hopefully this helps with #91
This commit is contained in:
Lovell Fuller
2014-09-25 10:07:26 +01:00
parent 150971fa92
commit 513b07ddcf
3 changed files with 38 additions and 0 deletions
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16
src/sharp.cc
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@@ -161,6 +161,19 @@ sharp_calc_crop(int const inWidth, int const inHeight, int const outWidth, int c
return std::make_tuple(left, top);
}
/*
Does this image have an alpha channel?
Uses colourspace interpretation with number of channels to guess this.
*/
static bool
sharp_image_has_alpha(VipsImage *image) {
return (
(image->Bands == 2 && image->Type == VIPS_INTERPRETATION_B_W) ||
(image->Bands == 4 && image->Type != VIPS_INTERPRETATION_CMYK) ||
(image->Bands == 5 && image->Type == VIPS_INTERPRETATION_CMYK)
);
}
/*
Initialise a VipsImage from a buffer. Supports JPEG, PNG and WebP.
Returns the ImageType detected, if any.
@@ -228,6 +241,7 @@ struct metadata_baton {
int height;
std::string space;
int channels;
bool has_alpha;
int orientation;
std::string err;
@@ -276,6 +290,7 @@ class MetadataWorker : public NanAsyncWorker {
baton->height = image->Ysize;
baton->space = vips_enum_nick(VIPS_TYPE_INTERPRETATION, image->Type);
baton->channels = image->Bands;
baton->has_alpha = sharp_image_has_alpha(image);
// EXIF Orientation
const char *exif;
if (!vips_image_get_string(image, "exif-ifd0-Orientation", &exif)) {
@@ -303,6 +318,7 @@ class MetadataWorker : public NanAsyncWorker {
info->Set(NanNew<String>("height"), NanNew<Number>(baton->height));
info->Set(NanNew<String>("space"), NanNew<String>(baton->space));
info->Set(NanNew<String>("channels"), NanNew<Number>(baton->channels));
info->Set(NanNew<String>("hasAlpha"), NanNew<Boolean>(baton->has_alpha));
if (baton->orientation > 0) {
info->Set(NanNew<String>("orientation"), NanNew<Number>(baton->orientation));
}