And if it overlaps something else, erasing can be incredibly hard. Once a line is established in a bitmapped format, the only thing you can do is erase it and start over. It’s the last two items that are very important for us. There are several advantages to the vector format: 1) specifying the line part of the arrow above requires 5 parameters, instead of 2500, 2) re-sizing an image is trivial (no matter the resolution, the geometric math remains the same), and 3) it’s easy to move the object (arrow or circle) around – simply re-specify the starting and/or ending points by dragging and dropping (the arrow is an object rather than a collection of pixels). There are similar algorithms for expressing the arrowhead type and size.įor the circle, one would specify the center point x,y coordinates, the radius, and the thickness. The beginning and ending x,y coordinate sets are called anchor points. In vector format, the line part would be specified by just five numbers: the starting x,y coordinates, the ending x,y coordinates, and a number specifying the thickness of the line (and information on color, where appropriate). Perhaps the straight line part of the arrow is 500 pixels across by 5 pixels down (2500 pixels, bitmapped). Vector graphics takes a different approach. Never export as JPG or PNG (unless it’s for unquantitative quick and dirty analysis, like in Trello). If you need to export as TIF, be sure to export at the highest depth supported (well, not higher than the collected data) and always export as uncompressed TIF. Basically, always keep the original data file, straight from the instrument. A gel is meant to be quantitative, so this loss of information is terrible for scientific data.įor gels, ALWAYS work with uncompressed TIF files, and always work with full “depth” files. JPG, PNG, and most TIF formats are compressed (AKA “lossy”) formats. High compression means combining/throwing away a lot of pixels. And of course, there are levels of compression (low to high) – at high compression the new file might be 10% of the size of the original. We want 16 bit or better (and be careful – you might read a 16 bit file into software and then unknowingly export it as 8 bit, throwing away data!).įor practicality, the default in photography is to “compress” the image by combining nearby pixels that are very close in intensity, in a way that the eye won’t notice. That’s not much “dynamic range” for science data. An uncompressed TIF would specify each and every pixel individually, resulting in a very large file.Īdd to that the “ depth” issue: in an 8 bit bitmapped grayscale image, each pixel can take on 256 levels of gray. A high resolution photograph might be 6000×4000 pixels. Photographs (and gels) are bitmapped – the format specifies a dot (or square) of varying intensity for each pixel. Zoomed in view a region of a gel – note the square pixels
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