diff options
Diffstat (limited to 'chapters/image.adoc')
| -rw-r--r-- | chapters/image.adoc | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/chapters/image.adoc b/chapters/image.adoc index e91b3da..07f5a0e 100644 --- a/chapters/image.adoc +++ b/chapters/image.adoc @@ -53,9 +53,16 @@ None [source,c++] ---- -// scale assert prevents int32_t accumulator overflow for in_t==int8_t +// shift assert prevents int32_t accumulator overflow for in_t==int8_t assert((resize_t == float_t && shift == 0)||(0 < shift && shift <= 11)); -assert(stride_x > 0 && stride_y > 0); +// stride asserts set consistent lower limit of 1/16 downscale +// independent of the shift value to simplify implementations +assert(0 < stride_x && stride_x < (16 << shift)); +assert(0 < stride_y && stride_y < (16 << shift)); +// offset range is similarly limited to maximum 16 pixels irrespective +// of shift. Both stride and offset fit in int16_t when shift=11. +assert((-16 << shift) < offset_x && offset_x < (16 << shift)); +assert((-16 << shift) < offset_y && offset_y < (16 << shift)); for_each(0 <= n < N, 0 <= oy < OH, 0 <= ox < OW; 0 <= c < C) { unit = (resize_t == float_t) ? 1.0 : (1 << shift); y = oy * stride_y + offset_y; |