This function implements the reverse blend described by Mark Ransom, for an additional small but visible improvement: reverseBlend[img_Image, alpha_Image, bgcolor_] := With[ {c = ImageData[img], a = ImageData[alpha] + 0.0001, (* this is to minimize ComplexInfinitys and considerably improve performance *) bc = bgcolor}, ImageClip@ Image[Quiet[(c – bc (1 – a))/a, {Power::infy, Infinity::indet}] /. {ComplexInfinity … Read more
Let’s assume our slow function has the signature f[x, y]. Pure In-memory Approach If you are satisfied with an in-memory cache, the simplest thing to do would be to use memoization: Clear@fmem fmem[x_, y_] := fmem[x, y] = f[x, y] This adds a definition to itself every time it is called with a combination of … Read more
Apart from etarion’s suggestion, you could also use the remap function. I wrote a quick script to show how you can do this. As you see coding this is really easy in Python. This is the test image: and this is the result after warping: And here is the code: import cv2 from scipy.interpolate import … Read more
I’ve found Waldo! How I’ve done it First, I’m filtering out all colours that aren’t red waldo = Import[“http://www.findwaldo.com/fankit/graphics/IntlManOfLiterature/Scenes/DepartmentStore.jpg”]; red = Fold[ImageSubtract, #[[1]], Rest[#]] &@ColorSeparate[waldo]; Next, I’m calculating the correlation of this image with a simple black and white pattern to find the red and white transitions in the shirt. corr = ImageCorrelate[red, Image@Join[ConstantArray[1, {2, … Read more
As others have pointed out, there are three ways to deal with errors in a consistent manner: correctly typing parameters and setting up conditions under which your functions will run, dealing correctly and consistently with errors generated, and simplifying your methodology to apply these steps. As Samsdram pointed out, correctly typing your functions will help … Read more
Here is a nice article. Also, FROM HERE (unchecked) Question: How do I modify the front end to add new keyboard shortcuts? Answer: (mathgroup May 2005, trevor baca:) I’ve been mucking around in KeyEventTranslations.tr setting up keyboard shortcuts recently and i’ve learned that front end tokens are pretty cool. this wolfram page gives pretty good … Read more
Todd Gayley (Wolfram Research) just send me a nice hack which allows to “wrap” built-in functions with arbitrary code. I feel that I have to share this useful instrument. The following is Todd’s answer on my question. A bit of interesting (?) history: That style of hack for “wrapping” a built-in function was invented around … Read more