raster-graphics

I can't find a way to explain the pixel array in the following situation: I created a BMP image 2x2 pixels with MS Paint on Windows 7. Saved it as monochrome BMP (which I think means BMP with color depth 1 bit per pixel) This is how the image looks like when zoomed it (black pixel, white pixel, white pixel, black pixel) Then I open the bmp with a hex editor and I can see the following info: 00: 424d 4600 0000 0000 0000 3e00 0000 2800 BMF.......>...(. 10: 0000 0200 0000 0200 0000 0100 0100 0000 ................ 20: 0000 0800 0000 0000 0000 0000 0000 0000 ................ 30: 0000 0000 0000 0000

For those who aren't familiar with the Gimp's "Color to Alpha" feature yet, here is the page on it from the Gimp's documentation: Color to Alpha . It does a really good job, and I wonder much how exactly Gimp does it in terms of color manipulation, whichever color space the colors might be in. Thanks a bunch for any hints. EDIT 1: Generating transparency information for a pixel based on its similarity to the key color (the one you select in the "Color to Alpha" dialog), like some folk suggested before removing his answer for some reason, would sound like a good insight, but I suppose it's more

I noticed some weird behavior when resizing the plot window. Consider library(sp) library(rgeos) library(raster) rst.test <- raster(nrows=300, ncols=300, xmn=-150, xmx=150, ymn=-150, ymx=150, crs="NA") sap.krog300 <- SpatialPoints(coordinates(matrix(c(0,0), ncol = 2))) sap.krog300 <- gBuffer(spgeom = sap.krog300, width = 100, quadsegs = 20) shrunk <- gBuffer(spgeom = sap.krog300, width = -30) shrunk <- rasterize(x = shrunk, y = rst.test) shrunk.coords <- xyFromCell(object = rst.test, cell = which(shrunk[] == 1)) plot(shrunk) points(shrunk.coords, pch = "+") If you resize the window, plotted