Re: Is QuickLook implemented upon CGImage or CGImageSource under the hood?
Re: Is QuickLook implemented upon CGImage or CGImageSource under the hood?
- Subject: Re: Is QuickLook implemented upon CGImage or CGImageSource under the hood?
- From: Mike Abdullah <email@hidden>
- Date: Fri, 07 Sep 2012 13:12:33 +0100
I would be surprised if QuickLook is bothering to use anything lower-level. The raw truth of it is that CGImageSource is intended to be the fastest image-decoding library on the Mac. Quick Look should have a possible benefit in raw speed because it might have already cached a file's thumbnail.
Of course, once you get into image manipulation, the story might change. What's your end goal here?
On 7 Sep 2012, at 13:02, Oleg Krupnov <email@hidden> wrote:
> I guess I should have asked "Is QuickLook implemented upon
> CGImageSource/CGImage or lower-level libraries under the hood?" I
> mean, the question is not I CGImageSource vs. CGImage, but rather
> CGImageSource/CGImage vs. lower-level libraries like libjpeg etc.
>
> I tried to measure the performance of QuickLook vs CGImageSource but
> it's hard to make a clean experiment. I keep getting different figures
> each time. At superficial glance, it seems that they show nearly equal
> performance.
>
> But it would be really curious what libraries QuickLook uses under the hood.
>
> Thanks!
>
> On Fri, Sep 7, 2012 at 2:09 PM, Mike Abdullah <email@hidden> wrote:
>> Your question in the subject makes little sense. CGImageSource is a means to
>> create CGImages. Quick Look likely uses both therefore.
>>
>> Ultimately, you need to test different image loading routes to see which
>> suits your needs.
>>
>> CGImageSourceCreateImageAtIndex
>> Generates full-size images as fast as it can
>>
>> QLThumbnailImageCreate
>> Generates thumbnails
>> Might have the thumbnail already cached for speed
>> Is going to spend a little time in cross-process communication
>> Logs warnings if used on the main thread in my experience
>> Can handle any file type, not just images
>>
>> CGImageSourceCreateThumbnailAtIndex
>> Generates thumbnails
>> Very fast
>>
>> On 7 Sep 2012, at 10:21, Oleg Krupnov <email@hidden> wrote:
>>
>> And what is the fastest method for image loading,
>> QLThumbnailImageCreate or CGImageSourceCreateImageAtIndex?
>>
>> Thanks!
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