JPEG_PlotTransformed (changes)
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Programmer's SpriteExtend Reference Manuals
» Part 11 – Sound and Video?SWI Calls
» JPEG_PlotTransformedJPEG?
» JPEG SWI Calls
» JPEG_PlotTransformed
JPEG_PlotTransformed
(SWI &49984)
| Entry | |
|---|---|
| R0 | Pointer to JPEG image in memory |
| R1 | Flags: |
| Bit 0: R2 is pointer to destination coordinates, else pointer to matrix | |
| Bit 1: Dither output | |
| Bit 2: Use full error diffused dithering | |
| Bit 4: Use colour mapping | |
| Bits 5-12: Translucency (0 = opaque, 255 = 1/256 visibility) | |
| Other bits reserved, should be zero | |
| R2 | Pointer to coordinate block or matrix, as defined by R0 |
| R3 | Length of data (bytes) |
| R4 | Pointer to Colour Mapping Descriptor, if relevant |
| Exit | |
|---|---|
| - | All registers preserved |
Use
This call is used to plot a transformed JPEG image to screen.
Notes
If R1 bit 0 is set, R2 is treated as a pointer to a Draw module Transformation Matrix describing the transform to apply to the image. If bit 0 is clear then R2 is treated as a pointer to a block giving the screen coordinates of a parallelogram to transform the image into:
| Word | Value |
|---|---|
| 0 | X0 coordinate, in 1/256th OS units |
| 1 | Y0 coordinate, in 1/256th OS units |
| 2 | X1 coordinate, in 1/256th OS units |
| 3 | Y1 coordinate, in 1/256th OS units |
| 4 | X2 coordinate, in 1/256th OS units |
| 5 | Y2 coordinate, in 1/256th OS units |
| 6 | X3 coordinate, in 1/256th OS units |
| 7 | Y3 coordinate, in 1/256th OS units |
Note that the default version of SpriteExtend supplied with RISC OS 5 does not support the plotting of transformed JPEGs. However it will perform a scaled plot if it detects that the transformation can be reduced to a set of scale factors compatible with JPEG_PlotScaled.
See also
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