To utilize the checkerboard pattern, for example, use: magick -size 640x480 pattern:checkerboard checkerboard. ImageMagick has a number of built-in images and patterns. PNG is a lossless format, so the -quality parameter only controls the zlib compression level any gains in image size will be minimal, but it's worth using. ImageMagick has no way to automagically determine the image format so we explicitly set one: magick -size 640x480 -depth 8 rgb:image image.png Built-in Images and Patterns. The format of the MinifyImage method is: Image MinifyImage(const. For example, here we resize both our images to a rough64圆4 size, or 4096 pixels in size. MinifyImage() is a convenience method that scales an image proportionally to half its size. This canbe used for example to make a collection of images of all different sizesroughly the same size. In your case, since you're starting with an already-rasterized image, this has no use. The 'at' symbol '', willresize an image to contain no more than the given number of pixels. However, your DPI should be a function of the output device you plan to use. Those formats are resolution-independant, so it makes sense to tell ImageMagick the DPI to which you want the image rasterized. "-density" won't help either, as it only works when "encoding a raster image while rendering (reading) vector formats such as Postscript, PDF, WMF, and SVG into a raster image". The amount of information is the same either way. For each image this command will produce a 1920x1080 version of the image, centered, with the edges padded in black where needed: convert input file -resize 1920x1080 -background black -gravity center -extent 1920x1080 output file Source: ImageMagick documentation for the -extent flag. The DPI value tends to correlate with image resolution, but is related only indirectly."ĭPI has nothing to do with getting a smaller file size your 100x100 image measures 100x100 pixels, no matter whether you see it on a 300dpi screen or a 96dpi one (it will just look smaller on the 300dpi screen). You can't do any better than that without a) coding to a lossy format (JPEG) or b) reducing the color depth of your image.įor a slightly longer explanation, straight from Wikipedia: "Dots per inch (DPI) is a measure of spatial printing or video dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm). I know that resizing the pictures dimension should get me below n at a certain point, but the process of resizing, saving, checking file size is cumbersome. The short version is, if you want a 100x100 image in PNG format, the line you have will already give you best quality at smallest file size. Every so often, I try to upload a picture to a website and encounter a message: Upload failed: the file size cant exceed n MB.
0 Comments
Leave a Reply. |