rotate bitmap based on exif orientation

[Bruno]

What's the best way to rotate a bitmap based on exif data?

This is the code that I came up with, but it's slow and I think there's a better way to do it... I need to basically load a bitmap and return it rotated.

any tips on how to make it better?

thanks!

static bool LoadImage(const std::string& file, SkBitmap* bitmap)

{

sk_sp<SkData> data = SkData::MakeFromFileName(file.c_str());

if (!data) return false;

std::unique_ptr<SkCodec> codec = SkCodec::MakeFromData(std::move(data));

if (!codec) return false;

SkImageInfo info = codec->getInfo().makeColorType(kN32_SkColorType);

if (!bitmap->tryAllocPixels(info)) return false;

if (codec->getPixels(info, bitmap->getPixels(), bitmap->rowBytes()) == SkCodec::kSuccess)

{

//checks if rotation is needed

if (codec->getOrigin() != kTopLeft_SkEncodedOrigin)

{

SkMatrix transform = SkEncodedOriginToMatrix(codec->getOrigin(), bitmap->width(), bitmap->height());

SkPath bounds; //this is a dummy path to hold the rotated image bounds

bounds.addRect(0.0f, 0.0f, static_cast<SkScalar>(bitmap->width()), static_cast<SkScalar>(bitmap->height()));

bounds.transform(transform);

SkBitmap rotated;

if (!rotated.tryAllocPixels(info.makeWH(static_cast<int>(bounds.getBounds().width()), static_cast<int>(bounds.getBounds().height()))))

return false;

SkCanvas canvas(rotated);

canvas.concat(transform);

canvas.drawBitmap(*bitmap, 0.0f, 0.0f);

canvas.flush();

*bitmap = rotated;

}

bitmap->setImmutable();

return true;

}

return false;

}

[Brian Osman]

If you use SkImageGenerator::MakeFromEncoded, the resulting SkImageGenerator object will handle the EXIF orientation for you. You can call getInfo to get the "real" (after rotation) dimensions, and getPixels will do the rotation of the pixel data for you.

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[Bruno]

thanks Brian!

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