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Implementation detail differences
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Implementation detail differences
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Filter Foundry tries to be as compatible with Filter Factory as possible.
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Filter Foundry tries to be as compatible with Filter Factory as possible.
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However, there are some differences that are explained in this documentation.
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However, there are some differences that are explained in this documentation.
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In Filter Foundry 1.7.0.8, the previously undocumented variables I, U, V as well as imin, umin, vmin
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In Filter Foundry 1.7.0.8, the previously undocumented variables I, U, V as well as imin, umin, vmin
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have been changed to represent the actual results of the i,u,v variables:
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have been changed to represent the actual results of the i,u,v variables:
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    I, imax = 255 (stayed the same)
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    imax = 255 (stayed the same)
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    U, umax = 55 (was 255 in Filter Factory)
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    umax = 55 (was 255 in Filter Factory)
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    V, vmax = 78 (was 255 in Filter Factory)
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    vmax = 78 (was 255 in Filter Factory)
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    imin = 0 (stayed the same)
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    imin = 0 (stayed the same)
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    umin = -55 (was 0 in Filter Factory)
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    umin = -55 (was 0 in Filter Factory)
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    vmin = -78 (was 0 in Filter Factory)
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    vmin = -78 (was 0 in Filter Factory)
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It is questionable if `I` was meant to be a synonym of `imax`, or if `I` was meant to be `I := imax - imin`.
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We have chosen the latter in Filter Foundry 1.7.0.9. Same thing with `U` and `V`.
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Therefore:
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    I := imax-imin = 255
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    U := umax-umin = 110
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    V := vmax-vmin = 156
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dmin, D (Testcase d_minmax.afs)
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**The Filter Factory manual writes:**
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0 corresponds to the 3 o'clock position
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256 to the 6 o'clock position,
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512 to the 9 o'clock position,
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768 to the 12 o'clock position,
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and 1024 to the full rotation back to the 3 o'clock position
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But this does not match the Windows implementation of Filter Factory
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(maybe it is true to the Mac implementation?)
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**In the original Windows implementation we can observe:**
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d=-512 is at 9 o'clock position
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d=-256 is at 12 o'clock position
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d=0 is at 3 o'clock position
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d=256 is at 6 o'clock position
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d=512 is the full rotation back to 3 o'clock position
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Therefore, `dmin` has been changed from 0 to -512,
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and `D`, `dmax` has been changed from 1024 to 512.
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get(i) (Testcase getput.afs)
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get(i) (Testcase getput.afs)
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Filter Foundry:
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Filter Foundry: