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Calculating Area of Scanned Image
Does anybody know of a windows program (maybe Excel) that would calculate the area (in pixels or any other unit) of a scanned image?
For example, if I were to draw circles on a sheet of paper, scan the paper into my computer, and then fill the circles with red paint in Microsoft Paint, is there a way to find out the area on the screen that the red paint occupies? I am hoping there may be a program that counts red pixels, for example. I tried to relate file size (in bytes) to amount of red paint, but there doesn't seem to be a relationship. If the files are saved as a bitmap, for example, they are all the same size regardless of the amount of color the image contains. If the files are saved as *.jpg, the file with less color turned out surprisingly larger. If I can quantify the amount of red color in any way, I will be able to convert into the units mm^2 because I can also scan a calibration square that is known to be 1 mm^2. Thanks a lot. Michael |
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Calculating Area of Scanned Image
Hi Michael.
You need an image processing program, such as Photoshop. This will give you a lot of information, for example the percentage of the image that is red. In a bitmap, the fact that a pixel is red or any other colour doesn't affect the file size - every pixel has the same amount of colour information and it only varies according to the number of colours that can be assigned to a pixel - eg 8, 16, 24 or 32 -bit. Also the resolution of the image affects file size. JPG assesses 8 x 8 pixel blocks in an image and assigns a single value to the most common colours in the block, using an affiine cosine transfromation algorithm. In short, it degrades the image by removing subtle colour tones. The higher the quality you choose when saving the file, the less degradation it does, and thus the best quality images are always larger files. Incidentally you notice a lot less degradation with files that have a majority of blue pixels 'cos the human eye can't detect as many shades of blue as it can any other colour... thus highly-compressed seascapes look better that the equivalently-compressd landscapes! Anyway, try Photoshop's image calculation routines, they should provide you with what you need. (I think Paintshop Pro may offer similar functionality, and it's cheaper!) HTH Phil "ntegrat61" wrote in message ... Does anybody know of a windows program (maybe Excel) that would calculate the area (in pixels or any other unit) of a scanned image? For example, if I were to draw circles on a sheet of paper, scan the paper into my computer, and then fill the circles with red paint in Microsoft Paint, is there a way to find out the area on the screen that the red paint occupies? I am hoping there may be a program that counts red pixels, for example. I tried to relate file size (in bytes) to amount of red paint, but there doesn't seem to be a relationship. If the files are saved as a bitmap, for example, they are all the same size regardless of the amount of color the image contains. If the files are saved as *.jpg, the file with less color turned out surprisingly larger. If I can quantify the amount of red color in any way, I will be able to convert into the units mm^2 because I can also scan a calibration square that is known to be 1 mm^2. Thanks a lot. Michael |
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