![]() This could be useful if your sticky note is tilted or rotated. You can streamline the above procedure (even transform it into an automatically working script if you want) even more, by converting the intermediate "canny-edges.png" into an SVG vector graphic, for example by running it through autotrace. To now cut the sticky note from the original image you can do: convert sticky-note.png (ImageMagick assumes the origin of its coordinate system the upper left corner of an image.) The width of the area is 246 pixels and the height is 190 pixels. # ImageMagick pixel enumeration: 1,300,255,srgbįrom above results you can conclude that the four pixel coordinates of the # ImageMagick pixel enumeration: 400,1,255,srgbĬonvert canny-edges.png -resize 1x300\! -threshold 50% txt:- \ Instead, I'll do a shortcut: I'll output the textual representation of the pixel color values to and directly grep it for all non-black pixels: convert canny-edges.png -resize 400x1\! -threshold 50% txt:- \ I'll not quote the contents of the new text files here, you can try it and look for yourself if you are interested. So we could introduce an additional -threshold 50% operation into our commands, to get pure black white output: convert canny-edges.png -resize 400x1\! -threshold 50% canny-1col.txtĬonvert canny-edges.png -resize 1x300\! -threshold 50% canny-1row.txt ![]() Here is part of the output from canny-1col.txt: # ImageMagick pixel enumeration: 400,1,255,grayĪs you can see, the detected edges from the text also influenced the grayscale values of the pixels. At the same time we'll change the output format to text, not PNG, in order to get the coordinates of these pixels which are white: convert canny-edges.png -resize 400x1\! canny-1col.txtĬonvert canny-edges.png -resize 1x300\! canny-1row.txt Now that the previous images visualized what the compression-resizing of an image into a few columns or rows of pixels will achieve, let's do it with a single column and a single row. ![]() Then you can resize an image into a 1xY column and a Xx1 row of pixels, where each pixel's color value is the average of the respective pixels of all pixels which were in the same row or same column as the respective column/row pixel.Īs an example which can be seen below, I'll first resize the new canny-edges.png to 4xY and Xx4 images: identify -format " %W x %H\n" canny-edges.pngĬonvert canny-edges.png -resize 400x4\! canny-4cols.pngĬonvert canny-edges.png -resize 4x300\! canny-4rows.png This command will create a black white image depicting all edges in the original image: convert \Īssuming the image is sized XxY pixels. Second stage: determine the coordinates of the edges.First stage: use canny edge detection to reveal the edges of the sticky note.It assumes the "sticky notes" are not tilted or rotated on the larger image: Here is the first algorithm which came to mind for me. There are different IM methods one can come up with.
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