🚀 go-pugleaf

In <1993Jan21.083211.3396@neptune.inf.ethz.ch> rofische@iiic.ethz.ch (Roman Fischer) writes:

>we are currently writting a game running under PM. The basic idea consists of
>two players simutaneiously fighting against a set of evil monsters. So we need
>lots (~20) of small bitmaps that move around the screen (window).
>The bitmaps were created with IconEdit and are loaded with GpiLoadBitmap. Since
>we need 4 versions of every monster (looking to the left, right, up and down),
>we need to "turn" the bitmaps. Because we don't want to change 4 bitmaps if
>we decide to change the look of a ghost, we decided to turn them "by software"
>at program-startup. So far no problem.

I want a copy when you're done!!!  :)

> <stuff deleted>
>The original size of the bitmaps is 20x20 pixels. When loading, we resize them
>to 36x36 pixels. Now, when reading the data into the buffer, the x-dimension
>is 40 !!!!

>This means: a. GpiQueryBitmapInfo returns a cx value of 36 (as expected).
>               But a short look at the data received from GpiQueryBitmapBits
>               shows, that every scan-line consists of 40 pixels (20 bytes).
>               
>            b. You cannot use cx to calculate the offset of a pixel.
>               To calculate the correct offset, you need to know the number
>               of bytes per scan-line.

>            c. If you don't know the original size of the bitmap, you cannot
>               tell the correct way to address a pixel within that bitmap !!

>Now:
>a. Did we miss an important part in any doc ? 

Yes, you did.  Bitmap bits are padded right to the next double-word boundary.

>b. Number of bytes per scan-line, any idea?

Use this formula (from the documentation) to calculate the number of bytes
per scanline needed:

HBITMAP hbmImage;
BITMAPINFOHEADER bihInfo;  /* Use BITMAPINFOHEADER2 if 32-bit app */
ULONG ulSzBuf;

GpiQueryBitmapParameters(hbmImage,&bihInfo);
ulSzBuf=(((bihInfo.cBitCount*bihInfo.cx)+31L)/32L)*4L*bihInfo.cPlanes;

If you have any questions, send me email.

Cheers,
Q
-- 
"If you choose not to decide, you  | "My other body is in the shop" - seen
 still have made a choice" - Rush  |  on a T-shirt
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