8/10/2023 0 Comments Gimp gradient magnitude![]() Layer 4: "Grid Layer" - 100 x 100 pixel grid, 1pxl wide lines, black Layer 3: "Drop Shadow Layuer" - Offset (X=0, Y=0), 23pxl, 80% opacity Layer 2: "Wall Background Layer" - Filled whole canvas with white and trimmed out the corridor area using the Fuzzy Select Tool (based on layer 1) ![]() Layer 1: "Wall Layer" (top) - 17pxl diameter paintbrush, black Please feel free to comment, critique, laugh at, and lend suggestions. ![]() If you look at some black and white images of real scenes, you can zoom in, look at individual pixel values, and develop a good sense of how these principles apply.I am trying my hand at a battle map/encounter map and I've put together a sample using Gimp along with all of the sample's attributes and my ultimate goal. The gradient will be steepest when it is perpendicular to the edge of the object. GradientAngle = arctan(gradientY / gradientX) You can then calculate the direction of the gradient as: Gradient magnitude and direction can be calculated using horizontal and vertical Sobel filters. The "true" edge point is the point at which slope is steepest along the gradient corresponding to the edge of an object. The blue line segment is a rough approximation of the slope of the curve at its steepest. The change isn't linear, but instead will look like one side of a bell curve: If we plot the brightness sampled along the arrow, we'll get something like the following plot, with red squares representing the brightness for a specific pixel. The red arrow shows the direction of the gradient from background to foreground: pixels are light on the left, and as we move in the +x direction the pixels become darker. The difference is that the gradient is located between two regions of constant color: white on the left, black on the right. If we zoom into the upper left corner of that box, we can see that there is a transition from white to black over just a few pixels. In image processing we can find those edges by looking at sharp transitions (sharp gradients) from one brightness to another. This is not obvious since you typically have to zoom into a photo to see the fuzzy edge. The pixel brightness does not change from black to white from one pixel to the next: there is a gradient that includes shades of gray. The edges are a bit fuzzy, but this is common in images of real objects. Here's an example of an object on a background. X-position (left to right), we get a plot that looks like this: If we plot the brightness of the gradient vs. This particular gradient is smooth, and we wouldn't say there is an "edge" in this image. The gradient is "linear" meaning that the change in intensity is directly proportional to the distance between pixels. Here's an example of a linear gradient from black (left) to white (right): You can create gradient images using software such as GIMP or Photoshop. ![]() In image processing, when we refer to a "gradient" we usually mean the change in brightness over a series of pixels. Paul R has given you an answer, so I'll just add some images to help make the point.
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