alphaData

Specifies the binary file that makes up the alpha channel of the picture in an image object.

# Metadata

Platforms: desktop, server, mobile OS: mac, windows, linux, ios, android Introduced: 1.1 Security:

# Syntax

set the alphaData of image to binaryData

# Examples

set the alphaData of image "Hellacious" to savedAlphaChannel

if charToNum(char x of the alphaData of image 1) is 255 then next repeat

# Description

Use the alphaData property to control the transparency of the pixels in an image.

Each pixel is represented by 8 bits (1 byte) of alpha channel data, with pixels numbered from the top left corner of the image, left to right, then top to bottom.

A value of zero means the pixel is fully transparent; a value of 255 is fully opaque; and values in between indicate a level of partial translucency.

>*Important:* Since the alphaData of an image is > binary file rather than text, trying to display the data > in a field may cause unexpected behavior.

Since each pixel is represented by 8 bits (1 byte or 1 character), you can obtain the numeric value for a given pixel using the charToNum function. For example, the numeric value of the alphaData for the tenth pixel is given by the expression charToNum(char 10 of the alphaData of image).

>*Important:* When changing the alphaData property, make sure the new > data is the correct size: 1 byte per pixel in the image. If you set an > image alphaData property to data whose total length is > incorrect, the image appearance may be distorted.

# Tags

multimedia,

# See

- **keyword:** field, image - **property:** maskData, blendLevel, pixels, imageData - **glossary:** property, binary file, pixel, expression, binary, alpha channel - **control structure:** function