Grid Pictures Modification

Geometrical Modifications

• Clip– Rectangular– Other shapes

• Rotate– Left, Right– 180 degrees– Flip

warping

warping

Morphing

Resolution modification

• Resolution / number of pixels /dimensions of picture

• Resolution Decreasing (average color of pixels)

• Resolution increasing - copying of pixels - dithering

Color depth decreasing

• Rounding of colors• Establishing of color palette• Half toning• Dithering

Half Toning

• Half tone matrix– example

0 12 3 15

8 4 11 7

2 14 1 13

10 6 9 5

Floyd Steinberg dithering

7/16

3/165/16

1/16

Pixel color correction

• Color correction• Saturation correction• Brightness correction

– Simple brightness correction– Contrast correction– Gamma correction

Saturation

S

Saturation correction

S

Brightness

Light

Brightness histogramm

K W

Color brightness

• Y = 0,299R + 0,587G + 0.114B

Simple brightness correction

Original br

New br

Simple brightness decreasing

Original br

New br

Contrast decreasing

Original br

New br

Contrast increasing

Original br

New br

Gamma correction of brightness

Original br

New br

Gamma function

Tedy

Y = 255 * (x/255)1/γ

Y = x1/γ

• Y = ymin + (ymax-ymin)*(x/xmax)1/γ

Gamma correctionOriginal

brightness On <0,1> γ=0,5 γ=2,2

0 0 0 0 0 0

10 0,039216 0,001538 0,392157 0,229437 58,50645

20 0,078431 0,006151 1,568627 0,314409 80,17437

60 0,235294 0,055363 14,11765 0,518046 132,1018

128 0,501961 0,251965 64,25098 0,731039 186,4151

200 0,784314 0,615148 156,8627 0,895449 228,3395

255 1 1 255 1 255