Bliting things with the "magic pink" color

Bliting things with the "magic pink" color

Felix-The-Ghost

Member #9,729

April 2008

In a sortof spriting program I have a temp bitmap to draw shapes and lines onto while they're being positioned, then I blit that on top of everything else but the problem is if I want this bitmap to have that color in it.
Instead of a temp I could draw directly to the screen but is that a bad idea? Wouldn't I have to hide the mouse and acquire the screen and such if I do that?

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]

someone972

Member #7,719

August 2006

I assume you mean that you are drawing a sprite containing lines and such over everything, but you want to be able to use magic pink as well as a color for the lines. The way I would do it is like this:

BITMAP* magic_pink_bitmap = create_bitmap_ex(8,BUFFER_W,BUFFER_H);
BITMAP* other_buffer = create_bitmap(BUFFER_W,BUFFER_H);

clear(magic_pink_bitmap); //clear to black: the default transparent color for 8-bit.
clear_to_color(other_buffer,makecol(255,0,255));
//...
if(color == makecol(255,0,255))
putpixel(magic_pink_bitmap,x,y,makecol8(255,0,255));
else putpixel(other_buffer,x,y,color);

draw_sprite(other_buffer);
draw_sprite(magic_pink_bitmap);

______________________________________
As long as it remains classified how long it took me to make I'll be deemed a computer game genius. - William Labbett
Theory is when you know something, but it doesn't work. Practice is when something works, but you don't know why. Programmers combine theory and practice: Nothing works and they don't know why. -Unknown
I have recklessly set in motion a chain of events with the potential to so-drastically change the path of my life that I can only find it to be beautifully frightening.

Edgar Reynaldo

Major Reynaldo

May 2007

You can cheat with the color and use makecol(254,0,254) - it's indistinguishable visually.

You can also just use a 32 bit bitmap with alpha instead. Clear it to transparent black and draw things opaquely, then use translucent drawing routines. You could also use alpha values as a binary transparency setting as well, and write your own drawing routine that ignores 0 alpha and writes non-0 alpha pixels.

Eagle and Allegro 5 binaries | Older Allegro 4 and 5 binaries | Allegro 5 compile guide
King Piccolo will make it so Then I could just flip it with some sweet, sweet matrix math. In either case, I’ll ride this wagon until the wheels fall off. Thanks to those that keep it running

Felix-The-Ghost

Member #9,729

April 2008

I want to avoid having other color depths, forgive me. Just a style I guess.
I have an idea kind of like yours, maybe draw the resembling color onto the bitmap and have a custom blit routine that reads each pixel ignoring the pink and for the special color writing that pink color instead so it's still that color but behind the scenes it works with a fake color. The dest bitmap is only 16x16 but I also draw a x2 copy and a x12 copy...would this be very slow? Doesn't the blit function read as well as write also?

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]

Audric

Member #907

January 2001

I think the shortest solution in terms of source code would be the 32bit temp bitmap : You can keep using 24bit for everything else, and allegro does transformations only when you write to it and when you blit it to your screenbuffer.
The two zoomed views can read from the normal view and stretch_blit() it, no problem of magic pink or alpha.

> The dest bitmap is only 16x16
Then do as you wish, it's impossible to get any performance problems with such a small area. The drawing program I'm working on (grafx2) does all drawing with the equivalent of putpixel/getpixel for allegro's BITMAPs, and the resultis still very smooth when using brushes much larger than your whole canvas.

Felix-The-Ghost

Member #9,729

April 2008

You can cross the different depths with each other? Would I still initialize with 24?

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]

Audric

Member #907

January 2001

Init with 24 since you want your "screen" to be 24 (and all memory bitmaps as well, by default) With create_bitmap_ex() you can precise for that one bitmap that you want 32bpp.
The manual for draw_trans_sprite() says:

Quote:

The bitmap and sprite must normally be in the same color depth, but as a special case you can draw 32 bit RGBA format sprites onto any hicolor or truecolor bitmap, as long as you call set_alpha_blender() first

Felix-The-Ghost

Member #9,729

April 2008

What happens if I draw in black (0,0,0) ?
Is the transparent black a different black?

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]

Thomas Fjellstrom

Member #476

June 2000

Quote:

Is the transparent black a different black?

Remember its an 8 bit only thing... And its not Black, its palette index 0. Which often tends to be set to black, but it may not be, and makecol may not generate index 0 for makecol(0,0,0) if there another black in the palette.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

Felix-The-Ghost

Member #9,729

April 2008

Wow I feel dumb for not understanding what you said.
You mean only in 8 bit black is transparent, yeah know that much, but you're saying that black is fine in 32 bit, but when converted it turns black?
So black's fine?

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]

Audric

Member #907

January 2001

In RGBA, any color with A=0 is fully transparent.
You'll want to fill your buffer with makeacol32(anything,anything,anything,0)
And then draw lines, pixels, etc. in makeacol32(R,G,B,255)
You can then draw_trans_sprite() this buffer, all colors are preserved, and transparent area is preserved as well.

Thomas Fjellstrom

Member #476

June 2000

Quote:

You mean only in 8 bit black is transparent, yeah know that much, but you're saying that black is fine in 32 bit, but when converted it turns black?

NO.

In 8 bit, you draw using indexes into an array (palette) of colors. The 8 bit number is replaced in the graphics card with the color in the palette that matches up with the 8 bit number. Palette entry 0 is generally "transparent", so any time the function that does the bliting encounters a 0, it skips it. Doesn't really matter what color is stored in the palette, it will be skipped.

Felix-The-Ghost

Member #9,729

April 2008

>In RGBA, any color with A=0 is fully transparent.
You'll want to fill your buffer with makeacol32(anything,anything,anything,0)
And then draw lines, pixels, etc. in makeacol32(R,G,B,255)
You can then draw_trans_sprite() this buffer, all colors are preserved, and transparent area is preserved as well.

Ugh. So I'll have to use those getr() etc if I already have a full color int...
Well needs a bit more but I should be able to get it.

==========================
<--- The ghost with the most!
---------------------------
[Website] [Youtube]