[bb] Convert 2 Antialiased Images into single image with alpha channel by Matty [ 1+ years ago ]

[BlitzBot]

Title : Convert 2 Antialiased Images into single image with alpha channel
Author : Matty
Posted : 1+ years ago

Description : This program was put together in response to a need I had to convert a model I'd rendered as a series of bitmaps in blitz3d into a format which had alpha information from antialiasing.  It requires 2 images - 1 with the anti aliased image against a white background and 1 with the anti aliased image against a black background.  It then creates a single TGA image with an alpha channel which retains the antialiasing information.  

Hopefully someone else may find a use for this.  Some of the code below comes from other people's code archives (notably the GetRed/GetBlue/GetGreen/GetRGB code and a few lines of the saveTGA code archive)

Code :

Code: BlitzBasic

1. ;Just a useful bit of code I put together as I needed to create some antialiased images from a model
2. ;rendered in blitz3d as I couldn't get the model I had into a renderer that would keep the animation which
3. ;I wanted to render out as anti aliased tgas.....
4. ;
5. ;
6. ;
7. ;
8. ;It is written in blitzplus but the only blitzplus specific code is the requestfile commands in the example
9. ;
10. ;The purpose of this program is to take 2 images with no alpha which have been anti aliased against both a
11. ;black and a white background and convert it into a single image with an alpha channel which retains the antialiasing
12. ;information in the alpha channel.  
13. ;
14. ;Seems to work fine for what I used it for.
15. ;
16. ;
17. ;
18. ;
19. ;
20. ;
21.  
22. Graphics 800,600,32,2
23.  
24. ;Supply your own images to test.
25.  
26. RGBBlack=GetColorMap(RequestFile("Anti Aliased Image File with Black Background","jpg;*.png;*.bmp"))
27. RGBWhite=GetColorMap(RequestFile("Anti Aliased Image File with White Background","jpg;*.png;*.bmp"))
28. CreateTGAWithAlpha(RequestFile("TGA Image With Alpha To Save","tga",True),RGBBlack,RGBWhite)
29. FreeBank RGBBlack
30. FreeBank RGBWhite
31. End
32.  
33.  
34. ;CODE
35.  
36.  
37.  
38. Function GetColorMap(FileName$)
39.  
40. image=LoadImage(FileName$)
41. If image=0 Then RuntimeError("Image Does Not Exist")
42. width=ImageWidth(image)
43. height=ImageHeight(image)
44. bank=CreateBank(8+width*height*4)
45. PokeInt bank,0,width
46. PokeInt bank,4,height
47. SetBuffer ImageBuffer(image)
48. LockBuffer
49. For y=0 To height-1
50. For x=0 To width-1
51. PokeInt bank,8+4*(x+y*width),ReadPixelFast(x,y)
52.  
53. Next
54. Next
55. UnlockBuffer
56. SetBuffer BackBuffer()
57. Flip
58. FreeImage image
59. Return bank
60. End Function
61.  
62. Function CreateTGAWithAlpha(FileName$,BlackImageBank,WhiteImageBank)
63. RGBBlack=BlackImageBank
64. RGBWhite=WhiteImageBank
65. If BlackImageBank=0 Or WhiteImageBank=0 Then RuntimeError("Need to pass white and black image banks")
66. If BankSize(BlackImageBank)<>BankSize(WhiteImageBank) Then RuntimeError("Black / White Image Banks should be the same size")
67. Width=PeekInt(BlackImageBank,0)
68. Height=PeekInt(BlackImageBank,4)
69. Offset=8
70. ImageBank=CreateBank(BankSize(BlackImageBank))
71. PokeInt ImageBank,0,Width
72. PokeInt ImageBank,4,Height
73. For Y=height-1 To 0 Step -1
74. For X=0 To Width-1
75. RGBBlack=PeekInt(BlackImageBank,8+4*(width*y+x))
76. RGBWhite=PeekInt(WhiteImageBank,8+4*(width*y+x))
77. DiffRed=GetRed(RGBBlack)-GetRed(RGBWhite)
78. DiffGreen=GetGreen(RGBBlack)-GetGreen(RGBWhite)
79. DiffBlue=GetBlue(RGBBlack)-GetBlue(RGBWhite)
80.  
81. AverageColorDifference=(Abs(DiffRed)+Abs(DiffGreen)+Abs(DiffBlue))/3
82. RGBAlpha=255-AverageColorDifference
83. If RGBWhite=RGBBlack Then RGBAlpha=255
84. If RGBBlack=GetRGB(0,0,0) And RGBWhite=GetRGB(255,255,255) Then RGBAlpha=0
85. PokeByte ImageBank,9+4*(x+((Height-1)-y)*width),getred(RGBBlack)
86. PokeByte ImageBank,10+4*(x+((Height-1)-y)*width),getgreen(RGBBlack)
87. PokeByte ImageBank,11+4*(x+((Height-1)-y)*width),getblue(RGBBlack)
88. PokeByte ImageBank,8+4*(x+((Height-1)-y)*width),RGBAlpha
89.  
90. Next
91. Next
92. f=WriteFile(FileName$)
93. If f=0 Then RuntimeError("Error Writing File")
94. ;Borrowed from Save TGA Example in Code Archives
95.         WriteByte(f,0) ;idlength
96.     WriteByte(f,0) ;colormaptype
97.     WriteByte(f,2) ;imagetype 2=rgb
98.     WriteShort(f,0) ;colormapindex
99.     WriteShort(f,0) ;colormapnumentries
100.     WriteByte(f,0) ;colormapsize
101.     WriteShort(f,0) ;xorigin
102.     WriteShort(f,0) ;yorigin
103.     WriteShort(f,width) ;width
104.     WriteShort(f,height) ;height
105.     WriteByte(f,32) ;pixsize
106.     WriteByte(f,8) ;attributes
107.         For offset=8 To BankSize(ImageBank)-4 Step 4
108.                 WriteByte f,PeekByte(ImageBank,offset+3)
109.                 WriteByte f,PeekByte(ImageBank,offset+2)
110.                 WriteByte f,PeekByte(ImageBank,offset+1)
111.                 WriteByte f,PeekByte(imagebank,offset)
112.        
113.         Next
114.  
115.         ;WriteBytes ImageBank,f,8,width*height*4       
116.  
117.  
118.  
119.  
120. CloseFile f
121.  
122. FreeBank ImageBank
123.  
124. End Function
125.  
126.  
127.  
128. ;From Code Archives
129. Function GetRGB(Red,Green,Blue)
130.  
131.  
132. Return Blue Or (Green Shl 8) Or (Red Shl 16)
133.  
134. End Function
135. Function GetRed(RGB)
136.  
137. Return RGB Shr 16 And %11111111
138.  
139. End Function
140. Function GetBlue(RGB)
141.  
142. Return RGB And %11111111
143.  
144. End Function
145. Function GetGreen(RGB)
146.  
147. Return RGB Shr 8 And %11111111
148. End Function

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