Help Using POINT

painintheworld

In trying to get back into the swings of things, I thought it prudent to start another small BASIC project, even though I have so many unfinished.

My thought was to put some text on the screen, from some custom stuff I worked out in Piskell. That font will be in three or four colors of gray, not far off from black, so as to make it look like something might be there, but barely. From there, I would simply scan down the screen from top to bottom, going from left to right as it goes down. Each pixel's color value would be checked using POINT ( px=POINT(x,y) ) . If px equaled one of the gray values from what I had drawn on the screen earlier, a SPRITE would be turned on (flipping through frames to look like it was sparkling) and then that pixel would be turned a shade of orange or red, depending on which gray color code was returned.

When trying this out, the values returned by POINT aren't making sense to me. Instead of the color code for the sample I just tried using COLOR 170 (SCREEN 14😛ALETTE 0), it is returning huge numbers. Black pixels are being returned as 4.27819008e+09. I've messed around with shifting bits, etc., but can't make any sense from the values returned by POINT. It is likely something simple that is going right over my head....but if someone could help me out, I would be most appreciative 🙂

Hawk

Ah bugger...I had almost finished my really detailed explanation of my investigation and I accidentally pressed Esc and lost it all! Fingers don't always do what I ask them to these days.

Anyway, here's the shorter version of my results.

I could replicate your results, and even when I set a different pixel color value, I got a slightly different floating point value.
But when I removed the PALETTE 0 command, an uninitialised pixel returned 4.27819008e+09, but an initialised pixel (ie. color 10 or 20) return the correct value.

Looking at the PSET command, the color value you set depends on the color space (PALETTE?). Maybe the POINT() command has the same dependancy. Maybe the value you are getting returned is an RGB value and needs to be converted to be printed correctly.

SCREEN 14
CLS
px=POINT(0,0)
PRINT"Value:";px
PSET 0,0,10
px=POINT(0,0)
PRINT"Value:";px

Edit:
I also wonder whether the floating point number is actually an RGB color. There doesn't seem to be a function to convert an RGB color back to separate RGB values.

painintheworld

Thank you, @Hawk !

I am back home now and will try setting all pixels to 0, run a quick test, and come back with an edit.

Edit: @Hawk nailed it! Using PALETTE 0 or 1 will return values that are not usable for me (at least for the moment). Using no PALETTE command or using PALETTE 2 allows POINT to return correct color values! Looks like I need to switch to true color!

Edit 2: Not sure about the FP numbers...there is most certainly a method to it 🙂 If anyone knows of RGB value conversions for PALETTE 0 and 1, a link would be much appreciated!

painintheworld

Yay, it works 🙂 Thank you again, @Hawk !

The code below is a shortened version of my test code. I retyped this truncated version, so it may have a bug.

Now, I need to see if I have some sparkly type sprite images. The broken laptop has an orange "font" (16x16 PNG tiles of letters & numbers) of sorts that was made in Piskell, using three (I think, it has been a while) shades of orange. Those shades of orange need to be changed to nearly black colors, so as to mostly mix in with the black background. As the POINT routine scans down and left to right, when/if it finds a particular shade, that shade will be replaced with a more fire-ish shade and the sparkly sprite will be turned on at that X/Y coordinate. Just thinking of an easy for me to implement title screen thing that would've been around in the early to mid-1980s, but a title screen that would've been required to have been written in assembly.

Edit: the version we are playing around in at home at the moment is searching for two different almost black colors, and doing it in loops similar to lines 250 through 310, except for one more condition, plus a little more stuff. The final will definitely need to be pared down in scope and optimized. Doing like I mention in this edit takes .393 seconds.

Edit 2: @Hawk the floating numbers do indeed represent RGB values. If you were to print the value from the variable ALMOSTBLACK, in line 150 below, you will get 4.28016387e+09 . Now to figure out how those numbers come to be 🙂

Edit 3: Ohhhh, evidently these are RGB plus alpha values! Have a great day and Happy New Year! Nearly 2:30 AM here and the wife wants to watch a movie, so I am off of here for now 🙂

100 SCREEN 14:PALETTE 2 110 TXT$=" SAMPLE TEXT " 113 ' using GPRINT and 8 px wide chars below, so get length * 8 114 ' & /2 for centering text 115 TXT=(LEN(TXT$)*8)/2 119 ' screen dimensions in X and Y 120 MAXX=PSIZE(0)-1:MAXY=PSIZE(1)-1 119 ' center x and center y 130 CX=MAXX/2:CY=MAXY/2 138 ' a yellow similar to 172 in palette 0 from my 139 ' initial tests 140 YELLOW1=RGB(255,213,0) 148 ' not as darkly colored as to what it will be 149 ' it is slightly visible for demo purposes 150 ALMOSTBLACK=RGB(30,30,30) 200 COLOR ALMOSTBLACK 208 ' CY-4 to center in Y axis and to take 8 px high 209 ' chars into account 210 GPRINT CX-TXT,CY-4,TXT$; 248 ' scanning entire screen for this demo only 249 ' final program needn't scan entire screen 250 FOR Y=0 TO MAXY 260 FOR X=0 TO MAXX 270 PX=POINT(X,Y) 280 IF PX=ALMOSTBLACK THEN 290 PSET X,Y,YELLOW1 295 ENDIF 300 NEXT X 310 NEXT Y