2.2.3.8 LevelsEffect Object

The LevelsEffect object specifies adjustments to the highlights, midtones, and shadows of an image.

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Highlight
MidTone
Shadow

Highlight (4 bytes): How much to lighten the highlights of an image. The color channel values at the high end of the intensity range are altered more than values near the middle or low ends, which means an image can be lightened without losing the contrast between the darker portions of the image.

Value	Meaning
0 ≤ value < 100	Highlights with a percent of intensity above this threshold SHOULD be increased.
100	Highlights MUST NOT change.

MidTone (4 bytes): How much to lighten or darken the midtones of an image. Color channel values in the middle of the intensity range are altered more than values near the high or low ends, which means an image can be lightened or darkened without losing the contrast between the darkest and lightest portions of the image.

Value	Meaning
-100 ≤ value < 0	Midtones are made darker.
0	Midtones MUST NOT change.
0 < value ≤ 100	Midtones are made lighter.

Shadow (4 bytes): How much to darken the shadows of an image. Color channel values at the low end of the intensity range are altered more than values near the middle or high ends, which means an image can be darkened without losing the contrast between the lighter portions of the image.

Value	Meaning
0	Shadows MUST NOT change.
0 < value ≤ 100	Shadows with a percent of intensity below this threshold are made darker.

Bitmap images are specified by EmfPlusBitmap objects (section 2.2.2.2).

See section 2.2.3 for the specification of additional image effects parameter objects.