December 2010
Intermediate to advanced
110 pages
2h 31m
English
Content preview from Canvas Pocket Reference
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Name
CRC.globalCompositeOperation — how colors are combined on the canvas
Synopsis
String globalCompositeOperation
Description
This property specifies how source pixels being rendered onto the
canvas are combined (or “composited”) with the destination pixels that
already exist in the canvas. This property is typically useful only when
you are working with partially transparent colors or have set the
globalAlpha property. The default is value is
“source-over”. Other commonly used values are “destination-over” and
“copy”.
The following table lists the allowed property values and their
meanings. In the third column, the word source
refers to the pixels being drawn onto the canvas, the word
destination refers to the existing pixels on the
canvas, and the word result refers to the pixels
that result from the combination of the source and destination. The
second column shows the formula for computing a result pixel from a
source pixel S and a destination pixel
D along with the alpha channel (the opacity) of the
source pixel αs and the alpha channel of the
destination αd:
| Value | Formula | Meaning |
|---|---|---|
copy | S | Draw the source pixel, ignoring the destination pixel. |
destination-atop | (1-αd)S +
αsD | Draw the source pixel underneath the destination. If the source is transparent, the result is also transparent. |
destination-in | αsD | Multiply the destination pixel by the opacity of the source pixel, but ignore the color of the source. |
destination-out | (1-αs)D | The destination pixel is made transparent when the source is ... |
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.