Difference between revisions of "Grey Scale Bitmaps"

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Grey scale is necessary for compatibility with Qbasic's legacy [[SCREEN (statement)|SCREEN]] modes when viewing 24/32 bit bitmaps! You may also desire grey scale images for aesthetic or artistic reasons.  
+
Grey scale is necessary for compatibility with QBasic's legacy [[SCREEN (statement)|SCREEN]] modes when viewing 24/32 bit bitmaps! You may also desire grey scale images for aesthetic or artistic reasons.  
  
 
* Set each color '''attribute''''s RGB '''intensities''' to the same value while incrementing the attribute values and intensity levels.  
 
* Set each color '''attribute''''s RGB '''intensities''' to the same value while incrementing the attribute values and intensity levels.  
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{{CodeStart}}
 
{{CodeStart}}
 
'' ''
 
'' ''
{{Cl|SUB}} True{{Cl|COLOR}}12 'Screen 12 greyscale of 24 bit 'code by Bob Seguin
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{{Cl|SUB}} TrueColor12 'Screen 12 greyscale of 24 bit 'code by Bob Seguin
 
{{Cl|IF}} BMP.PWidth * 3) {{Cl|MOD}} 4) {{Cl|THEN}}
 
{{Cl|IF}} BMP.PWidth * 3) {{Cl|MOD}} 4) {{Cl|THEN}}
 
ZeroPAD$ = {{Cl|SPACE$}}((4 - ((BMP.PWidth * 3) {{Cl|MOD}} 4)))
 
ZeroPAD$ = {{Cl|SPACE$}}((4 - ((BMP.PWidth * 3) {{Cl|MOD}} 4)))
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{{CodeStart}}
 
{{CodeStart}}
 
'' ''
 
'' ''
{{Cl|SUB}} True{{Cl|COLOR}}13   'Screen 13 greyscale of 24 bit 'code by Bob Seguin
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{{Cl|SUB}} TrueColor13   'Screen 13 greyscale of 24 bit 'code by Bob Seguin
 
{{Cl|IF}} ((BMP.PWidth * 3) {{Cl|MOD}} 4) <> 0 {{Cl|THEN}}
 
{{Cl|IF}} ((BMP.PWidth * 3) {{Cl|MOD}} 4) <> 0 {{Cl|THEN}}
 
ZeroPAD$ = {{Cl|SPACE$}}((4 - ((BMP.PWidth * 3) {{Cl|MOD}} 4)))
 
ZeroPAD$ = {{Cl|SPACE$}}((4 - ((BMP.PWidth * 3) {{Cl|MOD}} 4)))
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{{Cl|DO}}
 
{{Cl|DO}}
 
x = 0                                'set image to left side of screen
 
x = 0                                'set image to left side of screen
    {{Cl|DO}}
+
  {{Cl|DO}}
 
     {{Cl|GET}} #1, , B$
 
     {{Cl|GET}} #1, , B$
 
     {{Cl|GET}} #1, , G$
 
     {{Cl|GET}} #1, , G$
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     {{Cl|PSET}} (x, y), average            '3 * 255 divided by 3 = maximum color attribute of 255
 
     {{Cl|PSET}} (x, y), average            '3 * 255 divided by 3 = maximum color attribute of 255
 
     x = x + 1
 
     x = x + 1
    {{Cl|LOOP}} {{Cl|WHILE}} x < BMP.PWidth
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  {{Cl|LOOP}} {{Cl|WHILE}} x < BMP.PWidth
    {{Cl|GET}} #1, , ZeroPAD$                  'skip padder if used
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  {{Cl|GET}} #1, , ZeroPAD$                  'skip padder if used
    y = y - 1                            'move up one row from bottom
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  y = y - 1                            'move up one row from bottom
 
{{Cl|LOOP}} {{Cl|UNTIL}} y = -1
 
{{Cl|LOOP}} {{Cl|UNTIL}} y = -1
{{Cl|END}} {{Cl|SUB}} '' ''
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{{Cl|END SUB}} '' ''
  
 
{{CodeEnd}}
 
{{CodeEnd}}
  
  
<center>'''SCREEN [[_NEWIMAGE]]([[_WIDTH (function)|_WIDTH]] h&, [[_HEIGHT]] h&, 32) (24 BPP - 16 million colors)'''</center>
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<center>'''SCREEN [[_NEWIMAGE]](BMP.PWidth, BMP.PDepth, 32) (24 BPP - 16 million colors)'''</center>
 
{{CodeStart}}
 
{{CodeStart}}
  
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     y = y - 1                          'move up one row from bottom
 
     y = y - 1                          'move up one row from bottom
 
{{Cl|LOOP}} {{Cl|UNTIL}} y = -1
 
{{Cl|LOOP}} {{Cl|UNTIL}} y = -1
{{Cl|END}} {{Cl|SUB}} '' ''
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{{Cl|END SUB}} '' ''
  
 
{{CodeEnd}}
 
{{CodeEnd}}
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<center>'''Tinting Grey Scale Images'''</center>
 
<center>'''Tinting Grey Scale Images'''</center>
  
: To tint a SCREEN 12 or 13 greyscale image, keep the intensity settings of 1 or 2 colors less than the others.
+
: To tint a SCREEN 12 or 13 greyscale image, keep the '''palette''' intensity settings of 1 or 2 colors less than the others.
 
{{CodeStart}}
 
{{CodeStart}}
 
'' ''
 
'' ''
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{{CodeEnd}}
 
{{CodeEnd}}
  
: In 24/32 bit SCREENs, subtract some intensity from one or two of the 3 pixel settings.  
+
: In 24/32 bit SCREENs, subtract some intensity from one or two of the 3 '''image pixel''' settings.  
 
{{CodeStart}}
 
{{CodeStart}}
'' ''
+
'' ''  
{{Cl|GET}} #1, , B$
+
{{Cl|DO}}
    {{Cl|GET}} #1, , G$
+
  {{Cl|GET}} #1, , B$
    {{Cl|GET}} #1, , R$     
+
  {{Cl|GET}} #1, , G$
    red = {{Cl|ASC}}(R$)   
+
  {{Cl|GET}} #1, , R$     
    grn = {{Cl|ASC}}(G$)  
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  red = {{Cl|ASC}}(R$)   
    blu = {{Cl|ASC}}(B$)  
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  grn = {{Cl|ASC}}(G$)  
     IF red > Rtint THEN red = red - Rtint 'set one or 2 tint values less than others
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  blu = {{Cl|ASC}}(B$)     
    IF grn > Gtint THEN grn = grn - Gtint 'intensity values cannot be less than 0!
+
  average = (red + grn + blu) \ 3  'divide by 3 for average as colors match intensities
    IF blu > Btint THEN blu = blu - Btint 'use small tint values to minimize darkness
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  IF average > 5 THEN tint = 5 ELSE tint = 0
    average = (red + grn + blu) \ 3  'divide by 3 for average as colors match intensities
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  {{Cl|PSET}} (x, y), {{Cl|_RGB32}}(average - tint, average - tint, average) 'maximum color intensity = 255
    {{Cl|PSET}} (x, y), {{Cl|_RGB32}}(average, average, average) 'maximum color intensity = 255 '' ''
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  x = x + 1
 +
{{Cl|LOOP}} {{Cl|WHILE}} x < BMP.PWidth '' ''
  
 
{{CodeEnd}}
 
{{CodeEnd}}
 +
: You could keep the red and green intensity settings higher than blue to yellow, brown, or antique the image too.
  
  
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* [[Bitmaps]]
 
* [[Bitmaps]]
 +
* [[Icons and Cursors]]
  
  
  
 
{{PageNavigation}}
 
{{PageNavigation}}

Latest revision as of 13:11, 10 February 2021

Grey scale is necessary for compatibility with QBasic's legacy SCREEN modes when viewing 24/32 bit bitmaps! You may also desire grey scale images for aesthetic or artistic reasons.

  • Set each color attribute's RGB intensities to the same value while incrementing the attribute values and intensity levels.
  • Don't exceed 63 when using OUT in legacy screen modes 12 or 13. Screens 7 and 9 use DAC color settings.
  • Then set the color attributes to reflect the number of colors available in that legacy screen mode.
  • 24/32 bit do not use color attributes, so the intensity levels must be set to an average for all three.


SCREEN 12 (4 BPP - 16 colors)

SUB TrueColor12 'Screen 12 greyscale of 24 bit 'code by Bob Seguin IF BMP.PWidth * 3) MOD 4) THEN ZeroPAD$ = SPACE$((4 - ((BMP.PWidth * 3) MOD 4))) END IF n = 3 FOR Colr = 0 TO 15 '16 colors OUT &H3C8, Colr OUT &H3C9, n 'color intensities are each equal in grey scale OUT &H3C9, n OUT &H3C9, n n = n + 4 'increment intensities. maximum intensity = 63 NEXT Colr y = BMP.PDepth - 1: o$ = " " GET #1, BMP.Offset, o$ R$ = " ": G$ = " ": B$ = " " DO x = 0 'set image to left of screen DO GET #1, , B$ GET #1, , G$ GET #1, , R$ red = ASC(R$) 'intensities from 0 to 255 grn = ASC(G$) blu = ASC(B$) average = (red + grn + blu) \ 48 'divide by 16 colors and divide by 3 for average PSET (x, y), average '255 * 3 divided by 16 = maximum color of 15 x = x + 1 LOOP WHILE x < BMP.Pwidth GET #1, , ZeroPAD$ 'move up one row from bottom y = y - 1 LOOP UNTIL y = -1 END SUB


SCREEN 13 (4 or 8 BPP - 256 colors)

SUB TrueColor13 'Screen 13 greyscale of 24 bit 'code by Bob Seguin IF ((BMP.PWidth * 3) MOD 4) <> 0 THEN ZeroPAD$ = SPACE$((4 - ((BMP.PWidth * 3) MOD 4))) END IF FOR Colr = 0 TO 255 STEP 4 '63 different intensities FOR Reps = 0 TO 3 'set 3 colors at a time OUT &H3C8, Colr + Reps OUT &H3C9, n 'color intensities are each equal in grey scale OUT &H3C9, n OUT &H3C9, n NEXT Reps n = n + 1 'increment intensities. maximum = 63 NEXT Colr y = BMP.PDepth - 1: o$ = " " GET #1, BMP.Offset, o$ 'offset + 1 immediately after header R$ = " ": G$ = " ": B$ = " " DO x = 0 'set image to left side of screen DO GET #1, , B$ GET #1, , G$ GET #1, , R$ red = ASC(R$) grn = ASC(G$) blu = ASC(B$) average = (red + grn + blu) \ 3 'divide by 3 for average as colors match intensities PSET (x, y), average '3 * 255 divided by 3 = maximum color attribute of 255 x = x + 1 LOOP WHILE x < BMP.PWidth GET #1, , ZeroPAD$ 'skip padder if used y = y - 1 'move up one row from bottom LOOP UNTIL y = -1 END SUB


SCREEN _NEWIMAGE(BMP.PWidth, BMP.PDepth, 32) (24 BPP - 16 million colors)

SUB TrueGreyScale 'convert a 24 bit bitmap image to grey scale IF ((BMP.PWidth * 3) MOD 4) <> 0 THEN ZeroPAD$ = SPACE$((4 - ((BMP.PWidth * 3) MOD 4))) END IF y = BMP.PDepth - 1: o$ = " " GET #1, BMP.Offset, o$ 'offset + 1 immediately after header R$ = " ": G$ = " ": B$ = " " DO x = 0 'set image to left side of screen DO GET #1, , B$ GET #1, , G$ GET #1, , R$ red = ASC(R$) grn = ASC(G$) blu = ASC(B$) average = (red + grn + blu) \ 3 'divide by 3 for average as colors match intensities PSET (x, y), _RGB32(average, average, average) 'maximum color intensity = 255 x = x + 1 LOOP WHILE x < BMP.PWidth GET #1, , ZeroPAD$ 'skip padder if used y = y - 1 'move up one row from bottom LOOP UNTIL y = -1 END SUB


Tinting Grey Scale Images
To tint a SCREEN 12 or 13 greyscale image, keep the palette intensity settings of 1 or 2 colors less than the others.

FOR Colr = 0 TO 255 STEP 4 '63 different intensities FOR Reps = 0 TO 3 'set 3 colors at a time OUT &H3C8, Colr + Reps OUT &H3C9, n - tint 'decrease color intensities of red and green OUT &H3C9, n - tint OUT &H3C9, n 'higher blue intensity will blue the image NEXT Reps n = n + 1 'increment intensities. maximum = 63 IF n > 5 THEN tint = 5 'keep red and green intensity values above 0! NEXT Colr

In 24/32 bit SCREENs, subtract some intensity from one or two of the 3 image pixel settings.

DO GET #1, , B$ GET #1, , G$ GET #1, , R$ red = ASC(R$) grn = ASC(G$) blu = ASC(B$) average = (red + grn + blu) \ 3 'divide by 3 for average as colors match intensities IF average > 5 THEN tint = 5 ELSE tint = 0 PSET (x, y), _RGB32(average - tint, average - tint, average) 'maximum color intensity = 255 x = x + 1 LOOP WHILE x < BMP.PWidth

You could keep the red and green intensity settings higher than blue to yellow, brown, or antique the image too.


See also:




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