The first thing that many new users of Paint.NET learn about are layers. Sometime after that, they usually also discover that there are different ways that layers can be blended together. Today, I want to talk about two of the blending modes; multiply, and additive.
It helps to realize that each pixel (the dots that make up the picture) has 4 parts that make it a particular color and degree of transparency.
Color is a combination of three color channels with values from 0 (none of that color) to 255 (the brightest value of that color you can have). The color channels are the three primary colors of light (not pigment colors, light colors, which is important).
The three primary colors of light are red, green, and blue. Just as you can combine primary pigment colors (red, yellow, and blue) to make secondary colors (green, purple, and orange), you get secondary colors of light by combining red, green, and blue. The secondary colors of light are cyan (blue + green), magenta (blue + red), and yellow (red + green).
Lets make a little chart, so that we can see the color values (from 0 to 255) for primary and secondary colors (the numbers in each column represent red, green, and blue, also known as RGB):
red: 255 0 0
green: 0 255 0
blue: 0 0 255
cyan: 0 255 255
magenta: 255 0 255
yellow: 255 255 0
black is 0 0 0 (none of any color)
There is also a channel for how transparent a pixel is called "alpha", which also has a value from 0 (completely invisible) to 255 (completely opaque...can't see anything behind it).
When you use the various blend modes on a given layer, that blend mode determines how it affects the pixels in the layers below it. It's an additive thing, so it builds on the *result* of the blend modes and effects you've used on all of the layers beneath it.
The multiply blend mode generally allows for changing color and shading of things without obscuring them. It works like this:
Say we have a one-pixel image (play along, it's easier to explain this way). Your background layer is a red pixel (255 0 0).
You create a new layer, and fill it with blue(0 0 255), and then set the mode to multiply. Guess what color it turns...nope, not magenta. It turns black, and here's why.
This blend mode is named multiply for a reason. It takes each color value from the bottom layer and top layer and multiplies them together. Our two red values were 255 and 0, and (math coming) 255 x 0 is 0. Likewise, our two blue values were 0 and 255, and 0 x 255 is 0. For green, both values were 0, and 0 x 0 is 0. That means that our resulting color values are 0 0 0, which is black.
Normally, you're not adding two solid primary colors, so you won't end up with black. When you're starting with a medium grey bottom layer (127 127 127) and a blue top layer (0 0 255 with blend mode set to multiply), you'll end up with a darker blue (0 0 127).
The math for figuring out what value you'll get for each color goes like this:
((value a) X (value b)) / 255 = final value
So, our blue channel value becomes (255 X 127) / 255
That makes it 32385 / 255, after the multiplication, and then 127 after we divide.
Experiment a bit with "multiply" and different gradients (colored, black and white, radial, linear) on a layer above that with the mode set to multiply...it'll teach you a lot.
The Additive blend mode is a little simpler math-wise. Basically, your picture is going to end up brighter when you add a new layer with blend mode set to additive. As the name implies, you add each color value together to get the final value, maxing out at 255.
If you add a solid red (255 0 0) layer with blend mode set to additive to a solid blue (0 0 255) layer beneath, you do, indeed, get magenta (255 0 255).
The "opacity" slider in the layer properties will give you the full effect when it's all the way to the right, and no effect at all if it's all the way to the left. If you see a blend mode that looks interesting at full opacity, but just too overpowering, try adjusting that slider.
This explanation is meant to help you understand why you see the results you see when you use a particular blend mode. It doesn't cover how to achieve any particular effect, but hopefully, it helps you to understand why things changed the way they did when you used a particular blend mode.
Here are some examples with an image that contains some textures and details that you might normally see.
First, a gradient:
Then, some slightly blurry text:
Then, a base image to blend those with:
Multiply Blends
Gradient layer above the base image with mode set to multiply:
Text layer above the base image with mode set to multiply:
Additive Blends
Gradient layer above the base image with mode set to additive:
Text layer above the base image with mode set to additive:
drakaan
