Sep 29, 2014, 12:30

I don't know if this is right place for this.

When I hit Auto button in this plugin and apply later another filters I see that my photo had posterization effect. I search extensively what causes this problem and found out that poblem is in this plugin.

Whats going on? Show on example. After hitting auto button I get this value right below histogram (in line parameters: chanel; low; gamma; high):

Red; 28; 1.00; 224

Values in (colors channel) low other than 0, and high other than 255 causes posterization. This effect grows if sliders are far from their max position (for low - 0 and high - 255).

I think, that may be the solution for this problem:

1. Read min slider value and calculate differential betwen 0 and min slider value. Write down this value

2. Read slider max value and calculate differential betwen 255 and max slider value. Write down this value

3. Sum this both value and divide sum by 2. This is new gamma vaue for this channel.

Red value sample:

1. 28 - 0 = 28

2. 255 - 224 = 31

3. (28 + 31) / 2 = 59 / 2 = 29.5

Because you may enter only integers, your new value is 30. So you must enter in this channels values (in line parameters: chanel; low; gamma; high):

Red; 0; 1.30; 255

Do it in the same way in the Green and Blue channel.

Maybe you fix Levels plugin or do it in semiplugin mode? What do you think about this?

When I hit Auto button in this plugin and apply later another filters I see that my photo had posterization effect. I search extensively what causes this problem and found out that poblem is in this plugin.

Whats going on? Show on example. After hitting auto button I get this value right below histogram (in line parameters: chanel; low; gamma; high):

Red; 28; 1.00; 224

Values in (colors channel) low other than 0, and high other than 255 causes posterization. This effect grows if sliders are far from their max position (for low - 0 and high - 255).

I think, that may be the solution for this problem:

1. Read min slider value and calculate differential betwen 0 and min slider value. Write down this value

2. Read slider max value and calculate differential betwen 255 and max slider value. Write down this value

3. Sum this both value and divide sum by 2. This is new gamma vaue for this channel.

Red value sample:

1. 28 - 0 = 28

2. 255 - 224 = 31

3. (28 + 31) / 2 = 59 / 2 = 29.5

Because you may enter only integers, your new value is 30. So you must enter in this channels values (in line parameters: chanel; low; gamma; high):

Red; 0; 1.30; 255

Do it in the same way in the Green and Blue channel.

Maybe you fix Levels plugin or do it in semiplugin mode? What do you think about this?