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NAME
- BitMapScale
-
Perform raster scaling on a bit map. (V36)
SYNOPSIS
BitMapScale(bitScaleArgs)
void BitMapScale(struct BitScaleArgs *);
A0
FUNCTION
Scale a source bit map to a non-overlapping destination bit map.
INPUTS
- bitScaleArgs
-
structure of parameters describing scale: bsa_SrcX, bsa_SrcY - origin of the source bits.
- bsa_SrcWidth
-
see next
- bsa_SrcHeight
-
number of bits to scale from in x
- bsa_DestX
-
see next
- bsa_DestY
-
origin of the destination.
- bsa_DestWidth
-
see next
- bsa_DestHeight
-
resulting number of bits in x
- bsa_XSrcFactor
-
see next
- bsa_XDestFactor
-
equivalent to the ratio srcWidth:destWidth, but not necessarily the same numbers. Each must be in the range 1..16383.
- bsa_YSrcFactor
-
see next
- bsa_YDestFactor
-
equivalent to the ratio srcHeight:destHeight, but not necessarily the same numbers. Each must be in the range 1..16383.
- bsa_SrcBitMap
-
source of the bits to scale.
- bsa_DestBitMap
-
destination for the bits to scale. This had better be big enough!
- bsa_Flags
-
future scaling options. Set it to zero!
- bsa_XDDA
-
see next
- bsa_YDDA
-
for future use. Need not be set by user.
- bsa_Reserved1
-
see next
- bsa_Reserved2
-
for future use. Need not be set.
RESULT
The destWidth, destHeight fields are set by this function as described above.
NOTES
-
This function may use the blitter.
-
Overlapping source and destination bit maps are not supported.
-
No check is made to ensure destBitMap is big enough: use ScalerDiv to calculate a destination dimension.
BUGS
-
This function does not use the HighRes Agnus 'Big Blit' facility. You should not use XSrcFactor == XDestFactor, where SrcWidth or DestWidth > 1024.
-
Also, the blitter is used when expanding in the Y direction. You should not expand in the Y direction if ((DestX & 0xf) + DestWidth) >= 1024 pixels. (Up to 1008 pixels is always safe).