Saving Alpha Information To An Image

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Socoder -> Blitz -> Saving Alpha Information To An Image
Wed, 08 Aug 2007, 10:29
mike_g	I made some code to create a bumpmap of an image which works. I have a problem trying to save it to the high 8 bits of the image tho. As far as I can tell my code seems as if it should work. Is this not possible or something, or am I doing something wrong here? To run the code you need an image (preferably small) called 'test.bmp' in the same directory. ;-------------- GLOBALS ------------------; Const FILTER_W = 3 Const FILTER_H = 3 Const FACTOR# = 1.0 Const BIAS# = 128.0 Dim filter(FILTER_W, FILTER_H) ;------------- INIT FILTER ---------------; For y = 0 To FILTER_H-1 For x = 0 To FILTER_W-1 Read filter(x, y) Next Next Data -1, -1, 0 Data -1, 0, 1 Data 0, 1, 1 ;-------------- TEST PROG ----------------; Graphics 640, 480, 32, 2 SetBuffer BackBuffer() image = LoadImage("test.bmp") BumpMap(image) DrawImage image, 256, 0 DrawBump(image, 0, 0) WaitKey ;-----------------------------------------; Function BumpMap(image) hx = FILTER_W / 2 hy = FILTER_H / 2 w = ImageWidth(image) h = ImageHeight(image) SetBuffer ImageBuffer(image) LockBuffer For y=0 To h-1 For x=0 To w-1 r#=0: g#=0: b#=0 For fy=0 To FILTER_H-1 For fx=0 To FILTER_W-1 ix = (x-hx+fx+w) Mod w iy = (y-hy+fy+h) Mod h col = ReadPixelFast(ix, iy) r# = r# + GetRElement(col) * filter(fx, fy) g# = g# + GetGElement(col) * filter(fx, fy) b# = b# + GetBElement(col) * filter(fx, fy) Next Next r# = r# * FACTOR + BIAS g# = g# * FACTOR + BIAS b# = b# * FACTOR + BIAS If r# < 0 Then r# = 0 If r# > 255 Then r# = 255 If g# < 0 Then g# = 0 If g# > 255 Then g# = 255 If b# < 0 Then b# = 0 If b# > 255 Then b# = 255 col = col And 16777215 ;& out alpha bits alpha = ((r# * 61)+(g# * 174)+(b# * 21)) / 256 ;greyscale bumpmap alpha = alpha Shl 24 ;WRITE PIXEL BACK WITH NEW ALPHA INFO WritePixelFast(x, y, col+alpha) Next Next UnlockBuffer SetBuffer BackBuffer() End Function ;----------- RGB CONVERSION ----------------; Function GetRElement(col) Return (col Shr 16) And 255 End Function Function GetGElement(col) Return (col Shr 8) And 255 End Function Function GetBElement(col) Return col And 255 End Function Function ToRGB(r, g, b) Return (r Shl 16) + (g Shl 8) + b End Function ;------------- TEST FUNCTION ---------------; Function DrawBump(image, x_pos, y_pos) w = ImageWidth(image) h = ImageHeight(image) For y=0 To h-1 For x=0 To w-1 col = ReadPixel(x, y, ImageBuffer(image)) col = col Shr 24 col = ToRGB(col, col, col) WritePixel(x_pos+x, y_pos+y, col) Next Next End Function --v
Wed, 08 Aug 2007, 10:51
JL235	BlitzBasic doesn't support alpha components in images. \|edit\| After just testing it seems the alpha is always 255. Even after writing a number there. \|edit\|
Wed, 08 Aug 2007, 13:08
mike_g	Umm, yeah that kind of sucks dosent it :/ Oh well I guess I code recode it in C using SDL.
Wed, 08 Aug 2007, 13:53
JL235	If you can draw to texture buffers then you could use them. They support alpha channels. You could also make an array the same size as the image and use that to store the info. Or just make a second image and draw the greyscale bump mapping straight to it and miss out the alpha channels completely.
Wed, 08 Aug 2007, 15:23
Jayenkai	What exactly are you doing with the image afterwards? Leaving it in memory, or just using Blitz to create the alphas, for use in another project? -=-=- ''Load, Next List!''
Wed, 08 Aug 2007, 15:27
mike_g	@ Diablo: Yeah, I noticed that in the help file. I might have a play around with creating texture and see if that works. @Jay: I hadent really thought about that yet. Its just something I was playing around with for fun.
Wed, 08 Aug 2007, 15:33
Jayenkai	Your code works.. ;-------------- GLOBALS ------------------; Const FILTER_W = 3 Const FILTER_H = 3 Const FACTOR# = 1.0 Const BIAS# = 128.0 Dim filter(FILTER_W, FILTER_H) ;------------- INIT FILTER ---------------; For y = 0 To FILTER_H-1 For x = 0 To FILTER_W-1 Read filter(x, y) Next Next Data -1, -1, 0 Data -1, 0, 1 Data 0, 1, 1 ;-------------- TEST PROG ----------------; Graphics 640, 480, 32, 2 SetBuffer BackBuffer() image = LoadImage("test.png") BumpMap(image) DrawImage image, 256, 0 DrawBump(image, 0, 0) SaveTGA "Test.tga",image WaitKey ;-------------- Save image as TGA format ----------------; ; Tweaked from ; https://www.blitzbasic.com/codearcs/codearcs.php?code=1 Function SaveTGA(name$,texture) Local f,width,height,tbuffer,x,y width=ImageWidth(texture) height=ImageHeight(texture) f=WriteFile(name$) WriteByte(f,0) ;idlength WriteByte(f,0) ;colormaptype WriteByte(f,2) ;imagetype 2=rgb WriteShort(f,0) ;colormapindex WriteShort(f,0) ;colormapnumentries WriteByte(f,0) ;colormapsize WriteShort(f,0) ;xorigin WriteShort(f,0) ;yorigin WriteShort(f,width) ;width WriteShort(f,height) ;height WriteByte(f,32) ;pixsize WriteByte(f,8) ;attributes tbuffer=ImageBuffer(texture) LockBuffer tbuffer For y=height-1 To 0 Step -1 For x=0 To width-1 WriteInt f,ReadPixel(x,y,tbuffer) Next Next UnlockBuffer tbuffer CloseFile f End Function ;---------------------------------------------------------; Function BumpMap(image) hx = FILTER_W / 2 hy = FILTER_H / 2 w = ImageWidth(image) h = ImageHeight(image) SetBuffer ImageBuffer(image) LockBuffer For y=0 To h-1 For x=0 To w-1 r#=0: g#=0: b#=0 For fy=0 To FILTER_H-1 For fx=0 To FILTER_W-1 ix = (x-hx+fx+w) Mod w iy = (y-hy+fy+h) Mod h col = ReadPixelFast(ix, iy) r# = r# + GetRElement(col) * filter(fx, fy) g# = g# + GetGElement(col) * filter(fx, fy) b# = b# + GetBElement(col) * filter(fx, fy) Next Next r# = r# * FACTOR + BIAS g# = g# * FACTOR + BIAS b# = b# * FACTOR + BIAS If r# < 0 Then r# = 0 If r# > 255 Then r# = 255 If g# < 0 Then g# = 0 If g# > 255 Then g# = 255 If b# < 0 Then b# = 0 If b# > 255 Then b# = 255 col = col And 16777215 ;& out alpha bits alpha = ((r# * 61)+(g# * 174)+(b# * 21)) / 256 ;greyscale bumpmap alpha = alpha Shl 24 ;WRITE PIXEL BACK WITH NEW ALPHA INFO WritePixelFast(x, y, col+alpha) Next Next UnlockBuffer SetBuffer BackBuffer() End Function ;----------- RGB CONVERSION ----------------; Function GetRElement(col) Return (col Shr 16) And 255 End Function Function GetGElement(col) Return (col Shr 8) And 255 End Function Function GetBElement(col) Return col And 255 End Function Function ToRGB(r, g, b) Return (r Shl 16) + (g Shl 8) + b End Function ;------------- TEST FUNCTION ---------------; Function DrawBump(image, x_pos, y_pos) w = ImageWidth(image) h = ImageHeight(image) For y=0 To h-1 For x=0 To w-1 col = ReadPixel(x, y, ImageBuffer(image)) col = col Shr 24 col = ToRGB(col, col, col) WritePixel(x_pos+x, y_pos+y, col) Next Next End Function --v Blitz DOES work with Alphas.. It just doesn't PLAY with alphas.. And it also won't save them either.. Not sure about loading. So I grabbed a SaveTGA snippet from BB.com, and it's sorted. -=-=- ''Load, Next List!''
Wed, 08 Aug 2007, 15:57
mike_g	Nice one, cheers dude