Memblocks in AGK - GameCreators Forum

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anwserman

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Joined: 20th May 2011

Location: Wisconsin

Posted: 27th Mar 2013 22:14

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So I've been reading through the forums, and I noticed that the newest beta of AppGameKit offers Memblock access. I've never used memblocks before in DB Pro, so they're a completely new world for me. What I do know, however, is that they offer direct access to an image's raw data.

I read through some postings - and Cliff's image shrinker was quite informative - but I'm wondering how to manually change a pixel in an image. His code copies an image color from another part of the image. Let's say I wanted to replace a pixel at X, Y with pure white (RGBA 255,255,255,255)?

I saw how to split the byte to get the color parts but not the other way around, and I'm not sure how much code from DB can carry over to the AppGameKit world.

Thank you!

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Markus

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Posted: 27th Mar 2013 22:42 Edited at: 27th Mar 2013 22:49

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there are no direct image access. please correct me if i wrote wrong.

you can made a memblock from image, change a r,g,b,a (4 bytes) value and
make a image again. i think its not for realtime and not a direct access but usefuly for other things.
the memblock have a header with image size etc.

the functions in beta now:
CreateImageFromMemblock
CreateMemblock
CreateMemblockFromImage
DeleteMemblock
GetMemblockByte
GetMemblockExists
GetMemblockFloat
GetMemblockInt
GetMemblockShort
GetMemblockSize
SetMemblockByte
SetMemblockFloat
SetMemblockInt
SetMemblockShort

remstart
function SpecialImage(img,r2,g2,b2)

ImageWidth#=getimagewidth(img)
    ImageHeight#=getimageheight(img)

memBlockID=creatememblockfromimage(img)

x=0
    y=0

for x=0 to ImageWidth#-1
    for y=0 to ImageHeight#-1

// Finding The offset of a x,y pixel (The first 12 Bytes (3*4) are the headers : Width/Height/ColorDepth)
    offsetPix=12+((x+(y*ImageWidth#))*4)

// RGBA values :

r1=GetMemblockByte(memBlockID,offsetPix+0)
    g1=GetMemblockByte(memBlockID,offsetPix+1)
    b1=GetMemblockByte(memBlockID,offsetPix+2)
    a1=GetMemblockByte(memBlockID,offsetPix+3)

//r2=128
    //g2=0
    //b2=0
    a2=192

if (x>ImageWidth#*0.02 and x<ImageWidth#*0.95) and (y>ImageHeight#*0.15 and y<ImageHeight#*0.8) and a1<255

r3=(r2+r1)/2//-a1
        g3=(g2+g1)/2//-a1
        b3=(b2+b1)/2//-a1
        a3=(a2+a1)
        if r3<0 then r3=0
        if g3<0 then g3=0
        if b3<0 then b3=0
        if r3>255 then r3=255
        if g3>255 then g3=255
        if b3>255 then b3=255
        if a3>255 then a3=255

elseif (x>ImageWidth#*0.02 and x<ImageWidth#*0.95) and (y>ImageHeight#*0.15 and y<ImageHeight#*0.8) and a1=255
        //Volle Farbe mischen
        r3=(255+r2)/2
        g3=(255+g2)/2
        b3=(255+b2)/2
        a3=255
    else
        //Meine Farbe aber Alpha beibehalten!
        r3=r2
        g3=g2
        b3=b2
        a3=a1
    endif

setMemblockByte(memBlockID,offsetPix+0,r3)
    setMemblockByte(memBlockID,offsetPix+1,g3)
    setMemblockByte(memBlockID,offsetPix+2,b3)
    setMemblockByte(memBlockID,offsetPix+3,a3)

next
    next

createimagefrommemblock(img,memBlockID)
    deletememblock(memBlockID)

endfunction

remend

+ Code Snippet

remstart
function SpecialImage(img,r2,g2,b2)


    ImageWidth#=getimagewidth(img)
    ImageHeight#=getimageheight(img)

    memBlockID=creatememblockfromimage(img)

    x=0
    y=0

    for x=0 to ImageWidth#-1
    for y=0 to ImageHeight#-1

    // Finding The offset of a x,y pixel (The first 12 Bytes (3*4) are the headers : Width/Height/ColorDepth)
    offsetPix=12+((x+(y*ImageWidth#))*4)

    // RGBA values :

    r1=GetMemblockByte(memBlockID,offsetPix+0)
    g1=GetMemblockByte(memBlockID,offsetPix+1)
    b1=GetMemblockByte(memBlockID,offsetPix+2)
    a1=GetMemblockByte(memBlockID,offsetPix+3)

    //r2=128
    //g2=0
    //b2=0
    a2=192

    if (x>ImageWidth#*0.02 and x<ImageWidth#*0.95) and (y>ImageHeight#*0.15 and y<ImageHeight#*0.8) and a1<255

        r3=(r2+r1)/2//-a1
        g3=(g2+g1)/2//-a1
        b3=(b2+b1)/2//-a1
        a3=(a2+a1)
        if r3<0 then r3=0
        if g3<0 then g3=0
        if b3<0 then b3=0
        if r3>255 then r3=255
        if g3>255 then g3=255
        if b3>255 then b3=255
        if a3>255 then a3=255

    elseif (x>ImageWidth#*0.02 and x<ImageWidth#*0.95) and (y>ImageHeight#*0.15 and y<ImageHeight#*0.8) and a1=255
        //Volle Farbe mischen
        r3=(255+r2)/2
        g3=(255+g2)/2
        b3=(255+b2)/2
        a3=255
    else
        //Meine Farbe aber Alpha beibehalten!
        r3=r2
        g3=g2
        b3=b2
        a3=a1
    endif

    setMemblockByte(memBlockID,offsetPix+0,r3)
    setMemblockByte(memBlockID,offsetPix+1,g3)
    setMemblockByte(memBlockID,offsetPix+2,b3)
    setMemblockByte(memBlockID,offsetPix+3,a3)

    next
    next

    createimagefrommemblock(img,memBlockID)
    deletememblock(memBlockID)

endfunction

remend

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anwserman

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Posted: 27th Mar 2013 23:02

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Ooh that code snippit helps a lot! Thank you! And memblocks are the closest access to direct image manipulation we'll come across (better than nothing though!)

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anwserman

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Location: Wisconsin

Posted: 28th Mar 2013 21:18

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So I'm attempting this code to create a 512x512 Memblock and it's not working.

creatememblock(1, 1048588)
Setmemblockint(1, 0, 512)
Setmemblockint(1, 4, 512)
CreateImageFromMemblock(1, 1)

It crashes :/ Is there something I'm doing wrong? I think the Memblock is big enough and I'm trying to store the image size in it too at the first few bytes. Any ideas?

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Markus

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Posted: 28th Mar 2013 22:07

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the header is 12 bytes Width/Height/ColorDepth

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anwserman

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Posted: 28th Mar 2013 22:24

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Yup! (512 x 512 x 4) + 12 = 1048588. The color depth is assumed to be 32 any way, right? I wonder if the DB forums could be of assistance

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Matty H

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Joined: 7th Oct 2008

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Posted: 28th Mar 2013 22:58 Edited at: 28th Mar 2013 22:59

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You need to set the colour depth also:

+ Code Snippet

	unsigned int memSize = 12 + (_width * _height * 4);

	//-- Create memblock
	agk::CreateMemblock(m, memSize);
	agk::SetMemblockInt(m, 0, _width); 
	agk::SetMemblockInt(m, 4, _height);
	agk::SetMemblockInt(m, 8, 32);
	//-- Initialise memblock
	unsigned int currentOffset = 12;
	for(unsigned int i = 0; i < _width * _height; i++)
	{
		int r = 255;
		int g = 255;
		int b = 255;
		int a = 255;

		agk::SetMemblockByte(m, currentOffset, r);
		currentOffset++;
		agk::SetMemblockByte(m, currentOffset, g);
		currentOffset++;
		agk::SetMemblockByte(m, currentOffset, b);
		currentOffset++;
		agk::SetMemblockByte(m, currentOffset, a);
		currentOffset++;
	}

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