Imagemagic convert black background11/8/2023 ![]() ![]() The reference says this is more efficient and is the preferred method. We do not need the -alpha off mentioned in the reference, since JPG does not support any alpha channel. The result is the same as -background white -flatten. So starting with the original PNG, we do convert google.png -background white -alpha remove google_alpharemoveoff.jpg If I convert directly to raster PDF convert -density 200 test.pdf -distort SRT ' fx:int (rand ()2)-1' -compress zip testdet.pdf the conversion works. convert google_bg_white.png -flatten google_bg_white_flatten.jpgĪn alternate method to -flatten is to use -alpha remove, which is discussed. With this command line, the problem of dark background also affects the conversion to JPEG format. So one still needs to flatten the result, so that the antialiasing of the alpha channel will smoothly blend the colors near the boundaries. convert google_bg_white.png google_bg_white.jpg ![]() You have a nice clean background, but the image is still aliased (as it was in the original when the alpha channel was remove). However, if you simply remove the alpha channel the JPG will show aliasing since only the fully transparent pixels' background colors were changed to white. convert google.png -background white -alpha background google_bg_white.png It will look the very same as the original PNG. Often one will reprocess the original transparent PNG image so that it has some constant color underneath the alpha channel so that later one can remove the alpha channel and not have odd colors showing. You can see this with the mapping graph shown below, as I use the ' -negate ' operator on both the 'test' image and the standard IM 'rose' built-in image. That is, it will make the color red, its complementary color of cyan, and blue, yellow, etc. Simple Flatten (default background is white): convert google.png -flatten google_flatten.jpgįlatten with black background: convert google.png -background black -flatten google_flatten_black.jpg Essentially this makes white, black, and black, white,, adjusting all the colors to match. The stripes are from the underneath color below the alpha channel.Īlpha Channel (nicely antialiased): convert google.png -alpha extract google_alpha.jpg Turn alpha off: convert google.png -alpha off google_aoff.jpg PNG background : remove alpha and replace with white convert raw. However, the background color you use will change the appearance in transparent areas from that of the underneath color. I know of no significant issues using -background xx -flatten when converting PNG or GIF to JPG. PNG allows 8-bit transparency (partial transparent). GIF only allows binary transparency - fully transparent or fully opaque. But you should specify -background somecolor before -flatten, if you do not want the default background color. So you should use -flatten to properly do that conversion. JPG does not allow transparency and any transparent areas will show what color is underneath the transparency, which is often black. You can obviously view the BMP files on the PC to see what they should look like.Ģ-colour Palette is as good as you can expect.The problem with converting PNG to JPG is when the PNG has transparency. I would like to know whether Jean-Marc's sketch displays them on EPaper and how effectively. Prior to ImageMagick 6.4.7-0, -contrast-stretch will black-out at most. I don't know whether you own a colour TFT e.g. The default background color (if none is specified or found in the image) is. ![]() If anything, ImageMagick seems to produce a slightly better monochrome than IrfanView.Īlthough there is a lot to learn, the command line ImageMagick is much more powerful than a GUI. Magick convert marilyn-monroe-9412.jpg -resize 20% -compress none -type palette -dither FloydSteinberg -colors 2 -depth 1 marilyn_1.bmp magick convert tractor10.jpg -compress none -type palette -dither FloydSteinberg -colors 256 -depth 8 tractor_8.bmp I have improved my ImageMagick commands e.g. Not only does it produce RLE8 but the RLE8 files are bigger than uncompressed files! Most importantly the 256-colour BMP defaults to using RLE8 compression (which I don't support) Using the simple command produced rubbish BMP files. To identify the background color of an image using ImageMagick, we have a method named getImageBackgroundColor(). Magick tractor10.jpg -depth 8 -colors 256 tractor_8.bmp ImageMagick Examples Preface and Index Converting Color to Gray-Scale Image Level Adjustments. Magick tractor10.jpg -depth 4 -colors 16 tractor_4.bmp I have made a safer calculation for MCUFRIEND_kbv examples: if (bmpDepth >= depth įile.seek(imageOffset - (4WHITE and Blue->BLACK magick tractor10.jpg -depth 1 -colors 2 tractor_1.bmp ![]()
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