Scaling, Decimation (Subsampling)

This module resizes captured 8-bit color sensor images to fit the LCD display format. The resize module performs only downscaling. The same ratio is applied for both horizontal and vertical resize, then a fractional decimation algorithm is applied.

The decimation factor is a multiple of 1/16; values 0 to 15 are forbidden.

Table 1. Decimation Factor
Decimation Value	0–15	16	17	18	19	...	124	125	126	127
Decimation Factor	—	1	1.063	1.125	1.188	...	7.750	7.813	7.875	7.938

Table 2. Decimation and Scaler Offset Values
OUTPUT	INPUT	352 × 288	640 × 480	800 × 600	1280 × 1024	1600 × 1200	2048 × 1536
VGA 640 × 480	F	—	16	20	32	40	51
QVGA 320 × 240	F	16	32	40	64	80	102
CIF 352 × 288	F	16	26	33	56	66	85
QCIF 176 × 144	F	32	53	66	113	133	170

Example:

Input 1280 × 1024 Output = 640 × 480

Hratio = 1280/640 = 2

Vratio = 1024/480 = 2.1333

The decimation factor is 2 so 32/16.

Figure 1. Resize Examples