Is there a wrong contrast range in function description?

[scarl555]

Hi, this is the function description of brightnessContrast

// brightnessContrast adjusts the brightness and contrast of the image.
// The brightness value ranges between -1 .. 1, with 0 being neutral.
// The contrast value ranges between 0 .. 127, with 1 being neutral.
ImageData brightnessContrast(ImageData pixels, float brightness, float contrast)

if i'm looking into the function your contrast will be calculated like this:
contrastAdjust = -128*contrast + 128;
For a range from 0 to 127 i get values from 128 to -16.128. I uses the function parallel to PHP GD imagefilter. I create a live editing image with javascript and on save I generate an image with PHP and the images doesn't match. If I choose a range from 0 to 2 with 1 being neutral. I get values from 128 to -128 this machtes with the PHP imagefilter contrast range and I get two images they were very similar.

Is there a fault in my mind or in the function description?

Greetings
Simon

[kig]

Yep, if the code doesn't match the function description, we should change
one.

On 21 June 2016 at 12:50, scarl555 [email protected] wrote:

Hi, this is the function description of brightnessContrast

// brightnessContrast adjusts the brightness and contrast of the image.
// The brightness value ranges between -1 .. 1, with 0 being neutral.
// The contrast value ranges between 0 .. 127, with 1 being neutral.
ImageData brightnessContrast(ImageData pixels, float brightness, float
contrast)

if i'm looking into the function your contrast will be calculated like
this:
contrastAdjust = -128*contrast + 128;
For a range from 0 to 127 i get values from 128 to -16.128. I uses the
function parallel to PHP GD imagefilter. I create a live editing image with
javascript and on save I generate an image with PHP and the images doesn't
match. If I choose a range from 0 to 2 with 1 being neutral. I get values
from 128 to -128 this machtes with the PHP imagefilter contrast range and I
get two images they were very similar.

Is there a fault in my mind or in the function description?

Greetings
Simon

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