Creating and manipulating 3D anaglyphic images

Category:

Screen/Graphics

Type:

Snippets

Difficulty:

Beginning

Author: Anonymous

Version Compatibility: Visual Basic 6

More information:

Almost everyone is familiar with the standard 3D glasses (left:red, right:cyan), which are used in viewing anaglyphic images and movies. Anaglyphs are created using two separate images, one for the left eye and the other for the right. Below I will describe the methods of converting steroscopic image pairs to anaglyphs, and some things you can do with existing anaglyphs.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

CONVERTING STEREO PAIRS TO ANAGLYPHS:

First, you'll need the two images. You can find a bunch online if you search for "stereoscopic" or "jps" (Stereo JPEG). Once you have them, creating the 3D anaglyph is a snap. The idea is very simple: To create the new image, take the red from the left image, and the green and blue from the right. Easy, eh?

Example:
'''''''
Dim lX As Long
Dim lY As Long

For lX = 0 To New.Width -1
   For lY = 0 To New.Height -1
      New.Pixel(lX, lY).Red = Left.Pixel(lX, lY).Red
      New.Pixel(lX, lY).Green = Left.Pixel(lX, lY).Green
      New.Pixel(lX, lY).Blue = Left.Pixel(lX, lY).Blue
   Next lY
Next lX
'''''''

Simple!

A note, however. Heavy color saturation in the images can cause "ghost" effects. These are pieces of the image that show up to one eye and not the other. This is caused by too much red or cyan saturation in the image. For example, a bright red will show up very bright to the right eye, but very dark to the left eye. For this, the solution requires a loss of color information: reduce the color saturation, or even remove it entirely, from the source images. Grayscale works the best.

GRAYSCALING EXISTING COLOR ANAGLYPHS:

I've found many anaglyphs online that are spectacular except for a common problem: ghosts (see above). To help clarify things a little, I came up with a method of removing the color saturation from anaglyphs without discarding the red-cyan/left-right separation.
The idea is to create the left field using the existing red in the image, and the right field from the green. Meanwhile, you'll want to measure the brightness of each side so you can make them match later. If you don't do this, the right side will be too dark, and the same "ghosts" will appear, only in grayscale form.

Example:
'''''''
Dim bBitL() As Byte ' Left Values
Dim bBitR() As Byte ' Right Values
Dim lX As Long
Dim lY As Long
Dim lSumL As Long ' Left Total
Dim lSumR As Long ' Right Total
Dim nDif As Single

' First, seperate the values and total them...
Redim bBitL(0 To Src.Width - 1, 0 To Src.Height - 1)
Redim bBitR(0 To Src.Width - 1, 0 To Src.Height - 1)
For lX = 0 To Src.Width - 1
   For lY = 0 To Src.Height - 1
      bBitL(lX, lY) = Src(lX, lY).Red
      bBitR(lX, lY) = Src(lX, lY).Green
      lSumL = lSumL + Src(lX, lY).Red
      lSumR = lSumR + (bBitR(lX, lY) / 2) + (Src(lX, lY).Blue)
   Next lY
Next lX
' Second, calculate the average brightnesses...
lSumL = lSumL / (Src.Width * Src.Height)
lSumR = lSumR / (Src.Width * Src.Height)
lSum = (lSumL / 2) + (lSumR / 2)
' Third, check and repair brightness if needed...
If lSumL <> lSum Then
   nDif = lSum / lSumL
   For lX = 0 To Src.Width - 1
      For lY = 0 To Src.Height - 1
         bBitL(lX, lY) = FixBit(bBitL(lX, lY) * nDif)
      Next lY
   Next lX
End If
If lSumR <> lSum Then
   nDif = lSum / lSumR
   For lX = 0 To Src.Width - 1
      For lY = 0 To Src.Height - 1
         bBitR(lX, lY) = FixBit(bBitR(lX, lY) * nDif)
      Next lY
   Next lX
End If
' And, finally, build the new image...
For lX = 0 To Src.Width - 1
   For lY = 0 To Src.Height - 1
      New(lX, lY).Red = bBitL(lX, lY)
      New(lX, lY).Green = bBitR(lX, lY)
      New(lX, lY).Blue = bBitR(lX, lY)
   Next lY
Next lX
'''''''
And that FixBit() function, by the way...
'''''''
Public Function FixBit(Value)
   If Value < 0 Then Value = 0
   If Value > 255 Then Value = 255
   FixBit = Value
End Funcion
'''''''

And that's it!

AND SO ON AND SO FORTH:

In case you didn't think of it, you can tweak that grayscaling code to output two grayscale left and right images instead of creating a new anaglyph. This would be useful in creating JPS files from existing anaglyphs. Unfortunately, I pretty sure there isn't a way to separate an anaglyph into two color images, since the left image's green and blue values, and the right image's red value, were lost in the process that created the anaglyph in the first place (see the first bit about creating anagylphs).

So that's it! I don't know if anyone will find it useful, but no one else has submitted it. Enjoy =)