prog8/examples/cx16/imageviewer/koala_module.p8

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%target cx16
%import graphics
%import diskio
%import c64colors
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koala_module {
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const uword load_location = $6000
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sub show_image(uword filenameptr) -> ubyte {
ubyte load_ok=false
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if diskio.f_open(8, filenameptr) {
uword size = diskio.f_read(load_location, 2) ; skip the first 2 bytes (load address)
if size==2 {
size = diskio.f_read(load_location, 10001)
if size == 10001 {
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; set a better C64 color palette, the Cx16's default is too saturated
c64colors.set_palette_pepto()
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convert_koalapic()
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load_ok = true
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}
}
diskio.f_close()
}
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return load_ok
}
sub convert_koalapic() {
ubyte cy
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ubyte @zp cx
uword @zp cy_times_forty = 0
ubyte @zp d
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uword bitmap_ptr = load_location
; theoretically you could put the 8-pixel array in zeropage to squeeze out another tiny bit of performance
ubyte[8] pixels
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graphics.clear_screen(1, 0)
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for cy in 0 to 24*8 step 8 {
for cx in 0 to 39 {
for d in 0 to 7 {
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cx16.FB_cursor_position(cx as uword * 8, cy as uword + d)
get_8_pixels()
cx16.FB_set_pixels(pixels, 8)
}
}
cy_times_forty += 40
}
sub get_8_pixels() {
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ubyte bm = @(bitmap_ptr)
ubyte @zp m = mcol(bm)
pixels[7] = m
pixels[6] = m
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bm >>= 2
m = mcol(bm)
pixels[5] = m
pixels[4] = m
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bm >>= 2
m = mcol(bm)
pixels[3] = m
pixels[2] = m
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bm >>= 2
m = mcol(bm)
pixels[1] = m
pixels[0] = m
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bitmap_ptr++
sub mcol(ubyte b) -> ubyte {
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ubyte @zp color
when b & 3 {
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0 -> color = @(load_location + 8000 + 1000 + 1000) & 15
1 -> color = @(load_location + 8000 + cy_times_forty + cx) >>4
2 -> color = @(load_location + 8000 + cy_times_forty + cx) & 15
else -> color = @(load_location + 8000 + 1000 + cy_times_forty + cx) & 15
}
return color
}
}
}
}