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DstTransBltBM

Copy a block of system memory to a location in video memory with Bus Mastering and destination transparency.

Declaration

void NAPI GA_2DRenderFuncs::DstTransBltBM(
void *srcAddr,
N_int32 srcPhysAddr,
N_int32 srcPitch,
N_int32 srcLeft,
N_int32 srcTop,
N_int32 width,
N_int32 height,
N_int32 dstLeft,
N_int32 dstTop,
N_int32 mix,
GA_color transparent)

Prototype In

snap/graphics.h

Parameters

srcAddr | Address of source bitmap in system memory
srcPhysAddr | Physical address of source bitmap in system memory
srcPitch | Pitch of source bitmap in bytes
srcLeft | Left coordinate within source bitmap to copy
srcTop | Top coordinate within source bitmap to copy
width | Width of the rectangle in pixels
height | Height of the rectangle in scanlines
dstLeft | Left coordinate of destination
dstTop | Top coordinate of destination
mix | Mix code for the copy (GA_mixCodesType)
transparent | Transparent color value

Description

This routine will copy a bitmap from system memory with a physical starting address of srcPhysAddr to the destination rectangle (dstLeft, dstTop, dstLeft+width-1, dstTop+height-1) with the specified mix and with destination transparency. The mix code will be used to combine the source bitmap data with the pixels in the destination bitmap. The transparent color passed will be used to mask out pixels in the destination bitmap from being written. Where a pixel in the destination bitmap matches the transparent color, the pixel will be written to the destination bitmap. The srcPhysAddr value points to the start of the bitmap data in system memory as a physical memory address, not a linear memory address that the application software normally deals with. It is up to the calling application to use the necessary OS services to allocate a block of contiguous physical memory for the bitmap data, and to obtain the physical memory address to be passed into this function.

This version is different to the DstTransBltSys function in that the bitmap data is copied using Bus Mastering by the graphics accelerator, which allows this function to return before the copy has completed and the accelerator will complete the copy in the background with a DMA Bus Master operation. If this hardware supports Bus Mastering and this function is available, it will usually be the fastest method to copy a block of system memory to video memory.

Note that the srcLeft and srcTop coordinates define an offset within the source bitmap to be copied, so it will copy only a portion of the memory bitmap.

Note: Although you can achieve the same effect of this routine using the generic BitBltFxBM function, this function is provided separately as it is usually a workhorse function for sprite based game applications and needs to be as efficient as possible.

See Also

DstTransBlt, DstTransBltLin, DstTransBltSys, DstTransBlt, BitBlt, BitBltFx

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