M66335FP datasheet(21/59 Pages) RENESAS

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M66335FP

REJ03F0276-0200 Rev.2.00 Jun 16, 2008

Page 21 of 58

γ Correction

γ correction according to the sensitivity characteristics (logarithmic characteristics) of human eyes is implemented to

approximate the image data to natural images.

To do this, the M66335 writes the

γ correction table to the built-in SRAM and read the corrected values corresponding

to read image data values from the SRAM.

γ = 0.45 is considered to be the optimal for γ correction for thermal head printers. Figure 12 shows a characteristics

example at

γ = 0.45.

γ correction processing is set through the register 06: GAMMA as follows.

GAMMA: 00

γ = 1

GAMMA: 01

γ = conversion table value

GAMMA: 10

γ = 1 for image zone separation (character)

γ = conversion table value for image zone separation (photo)

GAMMA: 11

γ = conversion table value for image zone separation (character)

γ = 1 for image zone separation (photo)

For the procedures of inputting/outputting of data, refer to the section on writing to/reading from the

γ correction

memory.

Image data

A <5, 0>

(Address)

DO <5, 0>

(Output)

White

White:

Black

Black:

Data after

γ correction

γ = 1

γ = 0.45

γ correction memory

Image data (address)

Figure 12

γ Correction by Means of the Conversion Table

IF (Dlow

≤ DIN < Dup)

DOUT =

(

)

IF (Dup

≤ DIN)

DOUT = 1.0

IF (DIN < Dlow)

DOUT = 0

1.0

DOUT

1.0

Dlow

Dup

DIN

− Dlow

Dup

− Dlow

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