Entry
R0 = flags for desired operation:
bit 0 set => return dimensions, clear => don't return dimensions
all other bits reserved (must be zero)
R1 = pointer to buffer holding JPEG image
R2 = length of JPEG image, in bytes
Exit
R0 = returned information flags:
bit 0 set => greyscale image, clear => colour image
bit 1 set => transformed plots not supported, clear => supported
bit 2 set => pixel density is a simple ratio, clear => pixel density is in dpi
R1 preserved
R2 = width, in pixels (if R0 bit 0 set on entry)
R3 = height, in pixels (if R0 bit 0 set on entry)
R4 = x pixel density
R5 = y pixel density
R6 = SpriteExtend's additional extra workspace requirements to plot JPEG (0 => no additional extra workspace required)
This call gives information on a JPEG image held in a buffer in memory.
It checks the header enough to return the width and height, and does a partial validation of the data. It returns an error if the image appears to be invalid; if no error is returned you may assume the data is a JPEG image.
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