28.1.10  Blending images

The interp command interpolates two images linearly in the XYZ color space.

• interp takes three arguments:
  • img1, an image object with dimensions w₁× h₁ and color depth d₁.
  • img2, an image object with dimensions w₂× h₂ and color depth d₂.
  • t, a real number in [0,1].
• interp(img1,img2,t) returns the image with dimensions w× h and color depth d, obtained by linear interpolation between img1 and img2. The width an height of the resulting image are computed by solving the system of equations

  w h=(1−t)w1 h1+t w2 h2,  ln

  w h

  =(1−t)ln

  w1 h1

  +tln

  w2 h2

  .

  The resulting color depth d is the smallest one that is able to fit data from each image. For example, if img1 is a grayscale image with alpha channel (d₁=2) and img2 is a RGB image (d₂=3) with three channels and no alpha channel, then the resulting depth will be RGBA, i.e. d=4 (three color channels with alpha channel).

  To interpolate pixel data, interp first resizes both images to w× h. The RGB values of individual pixels are then computed by a perceptually uniform linear interpolation between the corresponding values in img1 and img2 (see Section 19.1.3).

Example

To begin, load two images:

Now blend the two images together with t=0.6: