WOLFRAM

Wolfram Language & System Documentation Center

ReplacePixelValue[image,pposval]

changes the pixel values at pixel position ppos in image to val.

ReplacePixelValue[image,pposval,"type"]

assumes val to be of the specified type.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Data  
Position  
Type  
Applications  
Properties & Relations  
See Also
Related Guides
History
Cite this Page

ReplacePixelValue

ReplacePixelValue[image,pposval]

changes the pixel values at pixel position ppos in image to val.

ReplacePixelValue[image,pposval,"type"]

assumes val to be of the specified type.

Details

  • ReplacePixelValue is typically used for image correction or annotation of 2D and 3D images by replacing pixel values at selected positions.
  • ReplacePixelValue assumes a pixel-aligned coordinate system that is shifted by 0.5 to the left and down with respect to the standard image coordinate system.
  • In ReplacePixelValue, integer coordinates correspond to the centers of the pixels. In 2D, pixel position represents the center of the bottom-left pixel. In 3D, pixel position corresponds to the center of the bottom-left front pixel.
  • Pixel positions ppos can be in one of the following forms:
  • {x,y} or {x,y,z}single position in 2D or 3D
    {xmin;;xmax,…}span of positions
    {xmin;;xmax;;xstep,…}span of positions with steps
    {pos1,pos2,…}a list of position specifications
    markerimagea marker image
  • ReplacePixelValue[image,{ppos1->val1,…}] can be used to set pixel values for multiple positions.
  • When the pixel position ppos lies on a boundary between pixels, all adjacent pixels are modified.
  • Pixel value val can be in one of the following forms:
  • sa scalar
    colora color
    {s1,s2,…}a list of channel values
  • Possible settings for "type" include:
  • "Bit"integer 0 or 1
    "Byte"integer 0 through 255
    "Bit16"integer 0 through 65535
    "Real32"single-precision real (32 bit)
    "Real64"double-precision real (64 bit)
  • ReplacePixelValue typically gives an image that has the same type as image.

Examples

open all close all

Basic Examples  (3)

Set a pixel in an image:

Wolfram Language code: ReplacePixelValue[[image], {2, 2} -> 1]

Replace a list of pixels in an image:

Wolfram Language code: ReplacePixelValue[[image], Table[{i, i} -> Hue[(i - 1) / 5] , {i, 6}]]

Specify the data type of the replacement value:

Wolfram Language code: ReplacePixelValue[[image], {2, 2} -> 255, "Byte"]

Scope  (12)

Data  (4)

Replace a value in a grayscale image:

Wolfram Language code: ReplacePixelValue[[image], {2, 1} -> 1]

Replace a value in a color image:

Wolfram Language code: ReplacePixelValue[[image], {1, 1} -> Yellow]

Replace a value in a grayscale 3D image:

Wolfram Language code: ReplacePixelValue[[image], {3, 1, 3} -> 0]

Set a pixel in the top-left front corner of a 3D color image to gray:

Wolfram Language code: ReplacePixelValue[[image], {1, 1, 3} -> Gray]

Position  (6)

Replace a single pixel value:

Wolfram Language code: ReplacePixelValue[[image], {1, 1} -> Cyan]

Replace pixel values at multiple positions:

Wolfram Language code: ReplacePixelValue[[image], {{1, 1} -> Cyan, {2, 1} -> Yellow}]

Replace multiple pixel values:

Wolfram Language code: ReplacePixelValue[[image], {{1, 1}, {2, 1}} -> Cyan]

Use Span to replace multiple pixel values:

Wolfram Language code: ReplacePixelValue[[image], {1 ;; 2, 1} -> Cyan]

Replace all pixels in a row:

Wolfram Language code: ReplacePixelValue[[image], {All, 3} -> Red]

Use a marker image to replace pixel values:

Wolfram Language code: ReplacePixelValue[[image], [image] -> Red]

Type  (2)

Replace a single pixel value:

Wolfram Language code: ReplacePixelValue[[image], {2, 1} -> Yellow]

Specify the data type of the replacement value:

Wolfram Language code: ReplacePixelValue[[image], {2, 1} -> {255, 255, 0}, "Byte"]

Applications  (2)

Replace black beans with red beans:

Wolfram Language code: ppos = PixelValuePositions[[image], RGBColor[{0.20392145216464996, 0.09019557386636734, 0.18039168417453766}], 0.16];
Wolfram Language code: ReplacePixelValue[[image], ppos -> RGBColor[{0.8156862745098039, 0.16862745098039217, 0.15294117647058825}]]

Extract pixel coordinates of handwritten annotations in a document:

Wolfram Language code: img = [image]; pos = PixelValuePositions[img, Red, 0.35];

Create a binary mask:

Wolfram Language code: mask = ReplaceImageValue[ConstantImage[Black, ImageDimensions[img]], pos -> White]

Remove the annotations:

Wolfram Language code: ReplacePixelValue[img, Dilation[mask, 1] -> White]

Properties & Relations  (3)

Any position within the bounds of a pixel may be used:

Wolfram Language code: ReplacePixelValue[[image], {3.35, 3.35} -> Red]

When the specified coordinate falls between pixels, all surrounding pixels are modified:

Wolfram Language code: ReplacePixelValue[[image], {2.5, 2.5} -> Red]

If a position outside of the image bounds is specified, no pixel is modified:

Wolfram Language code: ReplacePixelValue[[image], {{0.35, 0.35}, {3.65, 3.65}} -> Red]
Wolfram Research (2012), ReplacePixelValue, Wolfram Language function, https://reference.wolfram.com/language/ref/ReplacePixelValue.html (updated 2014).

Text

Wolfram Research (2012), ReplacePixelValue, Wolfram Language function, https://reference.wolfram.com/language/ref/ReplacePixelValue.html (updated 2014).

CMS

Wolfram Language. 2012. "ReplacePixelValue." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/ReplacePixelValue.html.

APA

Wolfram Language. (2012). ReplacePixelValue. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/ReplacePixelValue.html

BibTeX

@misc{reference.wolfram_2026_replacepixelvalue, author="Wolfram Research", title="{ReplacePixelValue}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/ReplacePixelValue.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_replacepixelvalue, organization={Wolfram Research}, title={ReplacePixelValue}, year={2014}, url={https://reference.wolfram.com/language/ref/ReplacePixelValue.html}, note=[Accessed: 13-June-2026]}