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Re: How to grab IconRef from a .tiff file.

On 8/21/03 3:31 PM, Mike Kluev didst favor us with:

> On 21/08/2003 21:33, Laurence Harris wrote:
>
>> Do you know of any way to draw *just* the alpha channel?
>
> I found the way, I just not sure it is the most straightforward way.
>
>> Awsome, Mike! Thanks.
>>
>> BTW, shouldn't that be LockPixels();
>>
>> instead of
>>
>> HLock((Handle)GetGWorldPixMap());
>
> No, this is for a reason. QuickDraw does LockPixels for you
> implicitly on every drawing operation, so it is not required.
> On the other hand the was still is (as I rechecked it just
> yesterday) a bug in QuickDraw that is caused by improper use
> of dereferenced unlocked pixmap handle. This bug is still
> clearly reproduced on 9 especially in case of picture recording.
> I am sure the bug is still there in X, although it doesn't
> reproduce itself because handles no longer move on X. So I
> always lock pixmap handle with HLock either the next line
> after creating GWorld or before CopyBits.

Okay, thanks. I didn't know about that.
>
>> I tried this and the other problem is that the result is the reverse of what
>> it should be. Is there more work involved or does it just need a different
>> copy mode than subOver?
>
> First make sure you get expected image when you open it in
> Preview app. It might be the case that this is alpha channel
> in the image is inverted for some reason.

Nope, it's a TIFF I created in Photoshop specifically for testing this code.

> If image is ok but
> you still get inverted result, put InvertRect(&r) after CopyBits.
>
That did it. Awesome!

Larry
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References: 
 >Re: How to grab IconRef from a .tiff file. (From: Mike Kluev <email@hidden>)



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