[mapserver-dev] Need help chopping Image into tiles using mapserver C code

[Stephen Woodbridge]

Resolved.

Daniel pointed out on IRC that I reverse the src and dest arguments in 
my call to msImageCopyMerge().  Duh!

Many thanks to Daniel,
   -Steve W


Stephen Woodbridge wrote:
> Hi all,
> 
> I'm writing some C code using Mapserver to generate an image and then 
> chop it into tiles and save the tiles. The basic flow is like:
> 
> 
>    oImg = msDrawMap(map, MS_FALSE);
>    ret = msSaveImage(NULL, oImg, szMetaImg); /* save/debug metatile */
> 
>    for tile rows {
>       for tile columns {
> 
>         oTile = msImageCreateGD(tileWidth, tileHeight, oImg->format, 
> NULL, NULL);
>         msImageCopyMerge(oImg->img.gd, oTile->img.gd, 0, 0, tileLeft, 
> tileTop, tileWidth, tileHeight, 100);
>         ret = msSaveImage(NULL, oTile, buf);
>         msFreeImage(oTile);
>       }
>    }
>    msFreeImage(oImg);
> 
> 
> My problem is that the metatile looks great, but all the tiles are 
> black. Traning through the mapserver code in msImageCopyMerge() it is 
> not using the gdImageCopyMerge() and running through the for loops.
> 
> Looping at the tile images in photoshop, it looks like the pixel values 
> are getting set to rgb(4,2,4), the background of the oImg, the src 
> image, id rgb(128,177,211)
> 
> Does anyone have a clue on what I am missing here?
> 
> -Steve W
> 
> in gdb oTile looks substantially like oImg
> 
> Breakpoint 2, main (argc=4, argv=0x7fffffccd268) at precache3ibeta2.c:860
> 860                                     oTile = 
> msImageCreateGD(tileWidth, tileHeight, oImg->format, NULL, NULL);
> (gdb) p oImg
> $1 = (imageObj *) 0x640870
> (gdb) p *oImg
> $2 = {width = 1680, height = 1680, imagepath = 0x63f880 "",
>   imageurl = 0x63f970 "", format = 0x60db80, imageextra = 0x1187b00,
>   buffer_format = 1, renderer = 0, size = 0, img = {gd = 0x6b4850,
>     svg = 0x6b4850, imagemap = 0x6b4850 "", raw_16bit = 0x6b4850,
>     raw_float = 0x6b4850, raw_byte = 0x6b4850 ""}}
> (gdb) p *oImg->format
> $3 = {name = 0x60dac0 "agg", mimetype = 0x60db20 "image/png",
>   driver = 0x60dbd0 "AGG/PNG", extension = 0x60db00 "png", renderer = 7,
>   imagemode = 1, transparent = 0, bands = 1, numformatoptions = 1,
>   formatoptions = 0x60dc10, refcount = 3, inmapfile = 1}
> (gdb) n
> 861                                     if (!oTile) {
> (gdb)
> 865                                     msImageCopyMerge(oImg->img.gd, 
> oTile->img.gd, 0, 0, tileLeft, tileTop, tileWidth, tileHeight, 100);
> (gdb) p *oTile
> $4 = {width = 200, height = 200, imagepath = 0x0, imageurl = 0x0,
>   format = 0x60db80, imageextra = 0x0, buffer_format = 0, renderer = 0,
>   size = 0, img = {gd = 0x11be030, svg = 0x11be030, imagemap = 0x11be030 
> "",
>     raw_16bit = 0x11be030, raw_float = 0x11be030, raw_byte = 0x11be030 ""}}
> (gdb) p *oTile->format
> $5 = {name = 0x60dac0 "agg", mimetype = 0x60db20 "image/png",
>   driver = 0x60dbd0 "AGG/PNG", extension = 0x60db00 "png", renderer = 7,
>   imagemode = 1, transparent = 0, bands = 1, numformatoptions = 1,
>   formatoptions = 0x60dc10, refcount = 4, inmapfile = 1}
> (gdb) p *oTile->format->formatoptions
> $6 = 0x60db60 "INTERLACE=false"
> 
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