Automatic alpha-map decals from grayscale images

[Risen]

I wish ZDoom's code would be changed so that it simply treats a grayscale graphic as an alpha decal (and if the DECALDEF for it has the "color" property set).

Seconded.

[HotWax]

First, how does ZDoom know that you're using a grayscale graphic? If it was to literally check the index number of the color against the known original palette, that would break the moment someone uses a custom palette.

How does the color property help clarify this? The wiki's entry on it is... less than helpful.

[Risen]

First, how does ZDoom know that you're using a grayscale graphic?

Read the appropriate PNG chunk, of course. IIRC, A palette isn't stored with grayscale images at all.

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From: http://java.sun.com/j2se/1.4.2/docs/api ... adata.html

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A PLTE chunk may not appear in a Gray or GrayAlpha image

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<!ATTLIST "IHDR" "colorType" ("Grayscale" | "RGB" | "Palette" | 
        "GrayAlpha" | "RGBAlpha") #REQUIRED>

How does the color property help clarify this?

The 'color' property defines what color the decal should be drawn in. An alpha-map must have a color defined, so leaving that property blank could default to drawing the decal as a grayscale image, in case that may have been the intended effect.

[Graf Zahl]

That would mean second-guessing an image's contents. That's why the setpng tool can be used to tag the images as alpha maps. I'm sorry but this shouldn't be done automatically.

[randi]

It's too bad the PNG specification does not have an official way to store an alpha channel without a color channel. Graf is right. There are perfectly valid reasons to store an image as grayscale, and the engine should not assume it's something else.

[Risen]

How about a new "alphamap" keyword for DECALDEF?