This translucency code is killing me

Bachus

Unregistered

Post: #1

Sep 18, 2002 — 07:10 AM

So I want to add the ability to draw sprites and tiles translucent. So rather than coming up with my own method, I thought I would just use BlitPixie, since BlitPixie rocks. The only real problem I saw was that my game uses GWorlds (ie, I'm not using SpriteWorld) and BlitPixie doesn't. So I created my own procedure to get the data I needed out of the GWorlds and then call the BlitPixie translucency code. And it almost works. When I copy an entire GWorld to another GWorld it works just fine. But when I try to copy just part of a GWorld to another it fails and draws nothing. I've been fiddling with the code for the past day and I just can't figure out what I'm missing. So if anybody can point out what I'm missing I'd be most appreciative.

Code:

void BlitTranslucent16(GWorldPtr srcGW, GWorldPtr destGW, Rect srcRect, Rect dstRect, unsigned short transLevel)

{    

    unsigned short *src;

    unsigned short *dst;

    PixMapHandle srcPixMapHandle = GetGWorldPixMap(srcGW);

    PixMapHandle dstPixMapHandle = GetGWorldPixMap(destGW);

    unsigned long srcRowBytes = (*srcPixMapHandle)->rowBytes & 0x3FFF;

    unsigned long dstRowBytes = (*dstPixMapHandle)->rowBytes & 0x3FFF;

    UInt16 *srcBaseAddr = (UInt16*)GetPixBaseAddr(srcPixMapHandle);

    UInt16 *dstBaseAddr = (UInt16*)GetPixBaseAddr(dstPixMapHandle);

    unsigned long    source, dest;

    unsigned short    alpha;

    short         i, j;

    short        width, height;    

    LockPixels(srcPixMapHandle);

    LockPixels(dstPixMapHandle);

    alpha = ((transLevel >> 8) & 0xFF);

    height = srcRect.bottom - srcRect.top;

    width = srcRect.right - srcRect.left;

    src = ((UInt16*)(srcBaseAddr + (srcRowBytes * srcRect.top) + (srcRect.left << 1)));

    dst = ((UInt16*)(dstBaseAddr + (dstRowBytes * dstRect.top) + (dstRect.left << 1)));

    srcRowBytes -= (unsigned long)(width << 1);

    dstRowBytes -= (unsigned long)(width << 1);

    for(j = 0; j < height; j++)

    {

            for(i = 0; i < width; i++)

         {            

            source = *src++;

            dest = *dst;

            if(source != 0x0000)    // Don't draw black

                BLEND_PIXELS_16( source, dest, alpha );

            *dst++ = dest;

        }

        src = (unsigned short *)((char *)src + srcRowBytes);

           dst = (unsigned short *)((char *)dst + dstRowBytes);

    }

    UnlockPixels(dstPixMapHandle);

    UnlockPixels(srcPixMapHandle);

}

Hog

Member

Posts: 151
Joined: 2002.09

Post: #2

Sep 18, 2002 — 08:28 AM

well, apart from the BLEND_PIXELS_16(...) part, the code sure seems to be working, make sure you actually set "dest"

ibullard

Unregistered

Post: #3

Sep 18, 2002 — 08:48 AM

I see nothing wrong with the code, but I suggest not accessing memory when you don't have to. Instead of reading dest in and then writing dest even when the pixel in transparent, try this:

Code:

        for(i = 0; i < width; i++)

         {            

            source = *src++;

            if(source != 0x0000)    // Don't draw black

            {

                dest = *dst;

                BLEND_PIXELS_16( source, dest, alpha );

                *dst = dest;

            }

            *dst++;

        }

Bachus

Unregistered

Post: #4

Sep 18, 2002 — 05:10 PM

So here's the working code:

Code:

void BlitTranslucent16(GWorldPtr srcGW, GWorldPtr destGW, Rect srcRect, Rect dstRect, unsigned short transLevel)

{    

    unsigned short *src = 0;

    unsigned short *dst = 0;

    unsigned short *srcRowStart = 0;

    unsigned short *dstRowStart = 0;

    PixMapHandle srcPixMapHandle = GetGWorldPixMap(srcGW);

    PixMapHandle dstPixMapHandle = GetGWorldPixMap(destGW);

    unsigned long srcRowBytes = (*srcPixMapHandle)->rowBytes & 0x3FFF;

    unsigned long dstRowBytes = (*dstPixMapHandle)->rowBytes & 0x3FFF;

    UInt8 *srcBaseAddr = (UInt8*)GetPixBaseAddr(srcPixMapHandle);

    UInt8 *dstBaseAddr = (UInt8*)GetPixBaseAddr(dstPixMapHandle);

    unsigned long    source, dest;

    unsigned short    alpha;

    short         i, j;

    short        width, height;    

    LockPixels(srcPixMapHandle);

    LockPixels(dstPixMapHandle);

    ForeColor(blackColor);

    BackColor(whiteColor);

    alpha = ((transLevel >> 8) & 0xFF);

    height = srcRect.bottom - srcRect.top;

    width = srcRect.right - srcRect.left;

    srcRowStart = ((UInt16*)(srcBaseAddr + (srcRowBytes * srcRect.top) + (srcRect.left << 1)));

    dstRowStart = ((UInt16*)(dstBaseAddr + (dstRowBytes * dstRect.top) + (dstRect.left << 1)));

    src = srcRowStart;

    dst = dstRowStart;

    for(j = 0; j < height; j++)

    {

        src = srcRowStart;

        dst = dstRowStart;

           for(i = 0; i < width; i++)

        {            

            source = *src;

            if(source != 0x0000)

            {

                dest = *dst;

                BLEND_PIXELS_16( source, dest, alpha );

                *dst = dest;

             }

            *src++;

            *dst++;

        }

         srcRowStart = (unsigned short *)((char *)srcRowStart + srcRowBytes);

         dstRowStart = (unsigned short *)((char *)dstRowStart + dstRowBytes);

    }

    UnlockPixels(dstPixMapHandle);

    UnlockPixels(srcPixMapHandle);

}

A bunch of little changes (made mostly for aesthetic reasons, none of them fixed the problem). What did fix it? Changing these two lines from this:

Code:

UInt16 *srcBaseAddr = (UInt16*)GetPixBaseAddr(srcPixMapHandle);

UInt16 *dstBaseAddr = (UInt16*)GetPixBaseAddr(dstPixMapHandle);

To this:

Code:

UInt8 *srcBaseAddr = (UInt8*)GetPixBaseAddr(srcPixMapHandle);

UInt8 *dstBaseAddr = (UInt8*)GetPixBaseAddr(dstPixMapHandle);

It's days like these that I hate programming.

Hog

Member

Posts: 151
Joined: 2002.09

Post: #5

Sep 19, 2002 — 02:34 AM

ofcourse i.e:
src = (UInt16*)(((UInt16*)srcBaseAddr) + (srcRowBytes * srcRect.top) + (srcRect.left << 1));
is just not the same as:
src = (UInt16*)(((UInt8*)srcBaseAddr) + (srcRowBytes * srcRect.top) + (srcRect.left << 1));

must have not noticed that.
if you want to make it look more aesthetic and avoid such problems in the first place you should write something like:

Code:

void BlitTranslucent16(GWorldPtr srcGW, GWorldPtr destGW, Rect srcRect, Rect dstRect, unsigned short transLevel)

{       

    UInt16 *src;

    UInt16 *dst;

    PixMapHandle srcPixMapHandle = GetGWorldPixMap(srcGW);

    PixMapHandle dstPixMapHandle = GetGWorldPixMap(destGW);

    UInt32 srcRowWidth = ((*srcPixMapHandle)->rowBytes & 0x3FFF)>>1;

    UInt32 dstRowWidth = ((*dstPixMapHandle)->rowBytes & 0x3FFF)>>1;

    UInt16 *srcBaseAddr = (UInt16*)GetPixBaseAddr(srcPixMapHandle);

    UInt16 *dstBaseAddr = (UInt16*)GetPixBaseAddr(dstPixMapHandle);

    UInt16    alpha,source;

    UInt16    i,j;

    UInt16    width, height;    

    LockPixels(srcPixMapHandle);

    LockPixels(dstPixMapHandle);

    alpha    = ((transLevel >> 8) & 0xFF);

    height    = srcRect.bottom - srcRect.top;

    width    = srcRect.right - srcRect.left;

    src = srcBaseAddr + srcRowWidth * srcRect.top + srcRect.left;

    dst = dstBaseAddr + dstRowWidth * dstRect.top + dstRect.left;

    srcRowWidth -= width;

    dstRowWidth -= width;

    for(j = 0; j < height; j++)

    {

        for(i = 0; i < width; i++)

        {            

            source = *src++;

            if(source)        // Don't draw black

                BLEND_PIXELS_16(source,*dst,alpha);

            dst++;

        }

        src += srcRowWidth;

        dst += dstRowWidth;

    }

    UnlockPixels(dstPixMapHandle);

    UnlockPixels(srcPixMapHandle);

}

Possibly Related Threads...

Thread:		Author	Replies:	Views:	Last Post
	Killing the char on the end of a char array	wyrmmage	3	2,960	Dec 4, 2006 08:55 PM Last Post: wyrmmage
	InvalWindowRect() is killing me!!	loki74	2	2,092	Jun 29, 2006 03:29 PM Last Post: loki74