Copy an image

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Fri, 2016-03-25 17:44

mritter0

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Last seen: 3 years 1 month ago

Joined: 2014-04-21 21:15

Copy an image

I have loaded an image with this

Object *
LoadInternalImage(STRPTR Render)
{
	return(IIntuition->NewObject(BitMapClass,NULL,
		BITMAP_SourceFile,					Render,
		BITMAP_Screen,						DefaultPubScreen,
		BITMAP_Precision,					PRECISION_EXACT,
		BITMAP_Masking,						TRUE,
	TAG_DONE));
}

Now I am trying to make a copy of it to keep the original and do some modifying to the copy. Everything I have tried loses the alpha transparency and it shows up pink. The image body is fine.

Object *
CopyImage(Object *SourceImg)
{
	Object							*Img;
	struct BitMap					*SourceBM, *DestBM;
	uint32							Width, Height, Depth, PixelFormat;
 
	if (SourceImg==NULL)
		return(NULL);
 
	IIntuition->GetAttrs(SourceImg,
		BITMAP_BitMap,						&SourceBM,
	TAG_DONE);
 
	Width=IGraphics->GetBitMapAttr(SourceBM,BMA_WIDTH);
	Height=IGraphics->GetBitMapAttr(SourceBM,BMA_HEIGHT);
	Depth=IGraphics->GetBitMapAttr(SourceBM,BMA_DEPTH);
//	Depth=IGraphics->GetBitMapAttr(SourceBM,BMA_BITSPERPIXEL);
	PixelFormat=IGraphics->GetBitMapAttr(SourceBM,BMA_PIXELFORMAT);
 
// I am forcing it to this format.  Either way has same result.
	if (!(DestBM=IGraphics->AllocBitMapTags(Width,Height,32,//Depth,
		BMATags_PixelFormat,				PIXF_A8R8G8B8,//PixelFormat,
		BMATags_Clear,						TRUE,
		BMATags_Displayable,				TRUE,
	TAG_DONE)))
	{
		return(NULL);
	}
 
// I have tried every combination, plus others.
	if (IGraphics->CompositeTags(
		COMPOSITE_Src,						SourceBM, DestBM,
//		COMPOSITE_Src_Over_Dest,			SourceBM, DestBM,
//		COMPTAG_Flags,						COMPFLAG_IgnoreDestAlpha,
//                              COMPTAG_Flags, COMPFLAG_SrcAlphaOverride | COMPFLAG_IgnoreDestAlpha,
//                              COMPTAG_Flags, COMPFLAG_SrcAlphaOverride,
	TAG_DONE) != COMPERR_Success)
	{
		IGraphics->FreeBitMap(DestBM);
 
		return(NULL);
	}
 
	if (!(Img=IIntuition->NewObject(BitMapClass,NULL,
		BITMAP_BitMap,						DestBM,
		BITMAP_Width,						Width,
		BITMAP_Height,						Height,
		BITMAP_HasAlpha,					TRUE,
		BITMAP_Screen,						DefaultPubScreen,
		BITMAP_Precision,					PRECISION_EXACT,
		BITMAP_Masking,						TRUE,
	TAG_DONE)))
	{
		IGraphics->FreeBitMap(DestBM);
 
		return(NULL);
	}
 
	return(Img);
}

What is happening to the transparency? The original image displays just fine, the copy does not (pink).

Thu, 2016-03-31 15:41

broadblues

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Last seen: 5 years 5 months ago

Joined: 2012-05-02 21:48

Re: Copy an image

The problem is the probably Composite call. CompoisteTags does a composite operation not a copy. Thus the alpha channel is not preserved, rather it's used to control the composite. A few people have been caught out by this.

It's not obvious to me what specific change you are trying to make with the Composite operation?

Fri, 2016-04-01 02:56

mritter0

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Last seen: 3 years 1 month ago

Joined: 2014-04-21 21:15

Re: Copy an image

That's the weird thing: CompositeTags() does "save" the alpha channel when loaded from a datatype. I use it a lot in my program. I load a BitMapClass with BITMAP_Render,"path", and such; AllocBitMapTags() a new bitmap; lock it and IDoMethod() pdtBlitPixelArrayBuffer to it, unlock it; AllocBitMapTags() another bitmap (destination); CompositeTags() with a scale down; create BitMapClass with destination bitmap and all it good.

I have tried with a mix and match of these tags with no luck, or worse results:

COMPTAG_Flags,						COMPFLAG_IgnoreDestAlpha,
COMPTAG_Flags, COMPFLAG_SrcAlphaOverride | COMPFLAG_IgnoreDestAlpha,
COMPTAG_Flags, COMPFLAG_SrcAlphaOverride,

But above I have already loaded the image to a BitMapClass and am copying the BITMAP_BitMap from it and the transparency gets lost; end up violet.

I am using CompositeTags() because I may need to scale it, so just have it ready to go (currently just copying it). I also tried to use BltBitMapTags() but has the same result: alpha is violet.

	IGraphics->BltBitMapTags(
		BLITA_Source,						SourceBM,
		BLITA_Dest,							DestBM,
		BLITA_SrcType,						BLITT_BITMAP,
		BLITA_DestType,						BLITT_BITMAP,
		BLITA_Width,						Width,
		BLITA_Height,						Height,
		BLITA_UseSrcAlpha,					TRUE,
	TAG_DONE);

So I would say it has something to do with the way GetAttrs() BITMAP_BitMap is getting the data, losing the alpha data along the way. ??????

Fri, 2016-04-01 03:55

(Reply to #3) #4

broadblues

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Last seen: 5 years 5 months ago

Joined: 2012-05-02 21:48

Re: Copy an image

BLITA_UseSrcAlpha, TRUE,

will alpha blend the src with the destination, that *will* lose the alpha component of the src, you want a straight copy with no blending.

But I have to say your approach is wrong. bitmap.image is not for loading images but displaying them (naturally it supports loading too, as a convenience).

If you want to load an image them modify it, use the datatype directly, then extact the 32bit bitmap, modify as required and create your new bitmap.image from it.

Tue, 2016-04-05 05:41

mritter0

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Last seen: 3 years 1 month ago

Joined: 2014-04-21 21:15

Re: Copy an image

I hear what you are saying about using datatypes to load the image, will try that later. For now, I I found another way to do what I need. I still need/want to get the copy to work, not giving up on it.

Sat, 2016-04-09 22:31

mritter0

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Last seen: 3 years 1 month ago

Joined: 2014-04-21 21:15

Re: Copy an image

I used the "traditional" method of loading the image with datatypes and BltBitMapTags(), got success.

Mon, 2016-04-11 18:09

(Reply to #6) #7

hypex

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Last seen: 2 months 2 weeks ago

Joined: 2011-09-09 16:20

Re: Copy an image

Just out of interest, did you also try copying the bitmap by grabbing a pointer to it and passing that along with BITMAP_BitMap as the source instead? Thus avoiding all the duplicating you were doing. If that could work.

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