pngflux.library, load and draw PNG w/ alphachannel

[thomas]

Originally Posted by AGS

Ah! And what about memory consumption for a picture of let us say screen size?

The alternative is to load the image with datatypes and apply the alpha channel with pngalpha.library. Then you would have the image in memory, the ARGB array and the alpha array. That's much more than with your library.

[thomas]

Originally Posted by AGS

needs only one multiplication

* 4 is a multiplication, too, isn't it?

[AGS]

LOL @ last two posts

this seems to work:

		move.l	pfo_Width(a0),d7
		mulu.w	d7,d3			; y * width
		ext.l	d2
		add.l	d2,d3			; + x
		lsl.l	#2,d3			; * 4 bytes (ARGB)

[AGS]

Ok, here is version 2.3:

http://images.quicktunnels.net/pngflux_v2.3.zip

Drawing functions are and work now like Thomas suggested.

- DrawArray
- DrawClip
- Draw

If everything is well I release the source.

NOTE: Yet only PNG in RGB format with or without alpha channel are supported! Loader returns ERROR_OBJECT_WRONG_TYPE with dos IoErr() when no match.


EDIT: Very little fix, had to copy the new library into the archive and fix the RGB format w/o alpha to work also (revision now set to 1). Please download again.

EDIT: Bugfix: didn't save registers in pngfDraw(), revision set to 2

EDIT: proper C includes

EDIT: speedup, revision set to 3

[thomas]

C files upated.

Maybe you could add a flag to the PNGFObject (and possibly an attribute for pngfGetAttr) which indicates that the loaded files did not have an alpha channel. Then, if the draw functions see this flag, they should revert to immediately call WritePixelArray resp. copy the data into the array without alpha blending. Perhaps the load routine can be so intelligent to set this flag also if there is an alpha channel but it is completely solid (i.e. all pixels are $ff).

[AGS]

Yes, I could add that, however I did not plan to make a full featured PNG library but only one for alpha ... but I think I add this ...

Thanks again for the includes.

[AGS]

/* Object returned by pfLoad(): */

struct PNGFObject {
	struct MinNode reserved;	/* Reserved, eventually for a list node */
	ULONG	pfo_Width;		/* You may find the width of the loaded
					   PNG image here. */
	ULONG	pfo_Height;		/* You may find the height of the lo.aded
					   PNG image here. */

	APTR	pfo_DrawBuffer;		/* PRIVATE */
	UWORD	pfo_DrawBufferModulo;	/* PRIVATE (actually width * 3) */
	ULONG	pfo_ARGBModulo;		/* PRIVATE (actually width * 4) */
	APTR	pfo_ARGBData;		/* PRIVATE. For compatibility always use
					   pfGetAttr() to read out this field. */
					
	UBYTE	pfo_EndHead;		/* End of the head, NOT of the Object!
					   Object size may vary:
	
					   DrawBuffer and ARGBData follow here,
					   so that alltogether can be freed with
					   one call to FreeVec(). */
	};

Is pfo_EndHead really an UBYTE? In my .i it is a LABEL.

Further, I removed all the funny fields from the object structure. Now it looks like this:

/* Object returned by pfLoad(): */

struct PNGFObject {
	struct MinNode reserved;	/* Reserved, eventually for a list node */
	ULONG	pfo_Width;		/* You may find the width of the loaded
					   PNG image here. */
	ULONG	pfo_Height;		/* You may find the height of the lo.aded
					   PNG image here. */
	APTR	pfo_ARGBData;		/* PRIVATE. For compatibility always use
					   pfGetAttr() to read out this field. */
					
	UBYTE	pfo_EndHead;		/* End of the head, NOT of the Object!
					   Object size may vary:
	
					   DrawBuffer and ARGBData follow here,
					   so that alltogether can be freed with
					   one call to FreeVec(). */
	};

I think this is the only place where to change that. So I did it.


PS: Is it possible to make the PRIVATE fields really private an not appear in the public struct?

[thomas]

Originally Posted by AGS

Is pfo_EndHead really an UBYTE? In my .i it is a LABEL.

I don't know what it's good for. A label is just another name for the field that follows. But there does not follow anything.

Is it possible to make the PRIVATE fields really private an not appear in the public struct?

No. The only way is obvious: just don't tell people where these fields are.

[AGS]

Does the "LABEL" type exist in C?

[thomas]

No.

[AGS]

so would it be ok if I remove that last line "pfo_EndHead" line from the C include completely? I mean it is only used by the library itself and that only from the pngflux.i (and I would also like to remove the pfo_ARGBData field also, it is only for internal purposes and there is the GetAttr()).

[AGS]

I built in a branch around the muls and divs in a pixel for the case that the alpha value of that pixel is $00 or $ff.

What about an "accuracy" parameter for the case someone is satisfied with a lsr instead of a divs?

[arti]

Any news about ABGR ?

[AGS]

I am not sure what you mean.

[arti]

An option to convert data to ABGR format because NetSurf shows wrong colors.

[mritter0]

Will this be usable with ReAction ButtonClass, LabelClass, etc. images?

LAYOUT_AddChild,			ChildObjects[GAD_IMAGE]=NewObject(ButtonClass,NULL,
    GA_ID,						GAD_IMAGE,
    GA_ReadOnly,				TRUE,
    BUTTON_BevelStyle,			BVS_NONE,
    BUTTON_Transparent,			TRUE,
    BUTTON_RenderImage,			ImgObjects[IMG_REQ_ARCHIVE],
TAG_END),

[AGS]

I am not sure what you mean but it looks like the answer is no or not yet.

[thomas]

It's a library, not a class, so no certainly it cannot be used with ReAction.

On the other hand, everything can be used with BOOPSI, you just need to write a class. Find an example attached.

[AGS]

I am impressed.

But in the file pngflux_ic.h there is maybe a typo:

	#define PngfluxObject NewObject(pngflux_class,NULL

I think a closing bracket ")" is missing.

Then, may I include this class somehow in the pngflux archive?

[thomas]

Originally Posted by AGS

I think a closing bracket ")" is missing.

Not, it's not. PngfluxObject is a macro which opens the NewObject call. Tags are then passed in the source code and finally there is EndObject macro which contains TAG_END and the closing bracket.

Then, may I include this class somehow in the pngflux archive?

I've cleaned up the code a bit, removed all the macros and PPC stuff. Now you can include it in your archive if you like.

Note: it is a piece of source code which compiles into an object module which is linked to the main program. It is not an external class as in Sys:Classes/Images.