I'm looking for an all-in-one solution for processing web images
Resizing
Cropping
Save as WEBP / JPEG / PNG
Drawing simple rectangles
Adding text
Reducing colors (quantization) for PNG
The only thing I'm not clear about is PNG quantization. Currently I'm using pngquant which works great, but I'd prefer to do everything in one place.
I see the SkiaSharp has SKImage.Encode() which takes a quality parameter. However there's no explanation as to what it actually is. Will this give me color quantization for PNG files? If not, is there something else in the library to do this?
Related
I downloaded this svg map and used ImageMagick to convert to PNG format. However, my output PNG images don't look very well: the white borders between countries almost don't show. On the other hand, the rendered versions on the Wikimedia site look great.
Is there any option I can pass to ImageMagick to prioritize borders?
Im trying to use pyreverse to generate UML images for a project source code. When I run the pyreverse command and specify to generate png images, it runs and then after a while, it shows:
dot: graph is too large for cairo-renderer bitmaps. Scaling by 0.271394 to fit
dot: graph is too large for cairo-renderer bitmaps. Scaling by 0.333083 to fit
Then if I open either image, the text is unreadable because it got scaled.
Is there a way to just not scale, and let the image be large size?
Thanks
the option
-T svg
worked for me
Cairo's maximum bitmap size is 32767x32767 pixels, and dot will scale your graph to fit inside that area. As an alternative, you can tell pyreverse to generate PDF files, and use some other tool to convert to PNG, if you really need bitmaps.
in 2019, you can simply output the diagram as svg using:
-o svg
I have some .bmp files that have some color (maybe black) that is supposed to show as transparent when the graphic is displayed on top a form, so the form color comes through the transparent areas. But by default, when I put these images in an Image View, the black/transparent areas show up as BLACK!
I'm thinking I need to either:
- alter how the NSImageView shows the image, so that a certain color is transparent, or
- modify the .bmp files somehow to make that color suitable for transparency in an NSImageView
But I don't know enough about graphics files, transparency(alpha), NSImageView, nor the image editing tools. I'm trying to use Gimp, but...not sure what I'm doing yet. It seems like there is already a color that should be transparent in the current .bmp file.
I'm sure its something simple for setting NSImageView, or editing my file, or perhaps making a mask for the image, but I don't know how yet. I've looked at various filters in IB for NSImageView, but have not found where to set the transparent color, nor how to grab that color from the image file to make sure I use the correct value.
Thanks in advance for any assistance. (I tried to post some images, but because I'm new, I could not.)
Beau
I'm not a Cocoa developer, but in Gimp try adding an alpha channel to your image (a layer mask, perhaps) then saving as a 32-bit PNG image (with an alpha channel), then load that PNG directly into your NSImageView. If you want to make the black pixels transparent in Gimp use the magic-wand tool to select them (use magic-wand with 0 tolerance) and just delete the contents of the selection then save as a PNG directly.
I have image.png in truecolor,
palette.png (N colors, where N>256) or text file, where list RGB color palette.
How to get a picture with this palette?
If I use imagemagick:
convert image.png -remap palette.png remap_image.png
It does not work.
convert image.png -map palette.png remap_image.png
Gives a very bad quality. The image is very noisy. File size is bigger than before.
GIMP gives best quality:
Сonvert image to indexed color > use custom palette
But GIMP is GUI. I need to convert a lot images in the console without running the gimp and X.org.
Using a shared palette across multiple images requires a carefully crafted palette. If you don't take great care when using the palette of a single image across many images, the result will be poor.
This needn't be complicated though. If you have accesss to the GIMP (or other tool) which supports truecolor graphics, you can create a large image and fit all of the smaller images into it, then quantize the image to N colors, then use that palette as the source.
you should be able to closely mimic GIMP's behavior in the console using ImageMagick
Once you've got a truecolor image with all the colors you want to quantize,
# Create an 8-bit png from our source, with a 235-color palette as an example.
convert truecolor_source.png -colors 235 palette.png
# Create an 8-bit png from an arbitrary image and use the palette in palette.png
convert sample.png -map palette.png output.png
There are a number of options for down-sampling colors, like dithering. See the ImageMagickv6 example page for an excellent overview with example pictures and code.
Although I still don't exactly understand what you want to do, your currently most recent comment ("Yes, from RGB to palette will set independently. Need set correct quantity of colors"), it sounds like all you want to do is set a strict limit on the amount of colors of a bunch of images, but they don't need to use the same palette.
In that case, the solution is very simple:
convert sample.png -colors 135 output.png
Try playing with the quantization options if the result isn't to your satisfaction.
If the output image is too large for your liking, you can experiment with the -quality option.
If this still isn't satisfactory, please try to explain your goal in a more detailed manner.
Good luck!
cat photo.png | pngnq -s 1 > photoindexed.png
I tend to get good results with the "-remap" (single imge) or "+remap" (multiple images) functions in combination with "-colors". Read up on those functions here. Note that "with "-remap" you provide IM with the final set of colors you want to use for the image, whether you plan to dither those colors, or just replace the ones with their nearest neighbours.", meaning just remapping/replacing might not look good enough, as colors from the input image are simply replaced by those from the palette image. Some form of dithering will be necessary to distribute pixel color conversion errors throughout the output image, because not all colors in the palette match those of the input image.
I'd suggest you use the "-colors N" option for that. This will reduce your output image color count to a maximum of N. By default ImageMagick uses "-dither Riemersma" for this implicitly when you specify "-colors N". The are also other dithering options available.
World Map Images in Adobe Illustrator CS5
I have an image Map in illustrator CS5 which i want to save in GIF so as to reduce its size for web use. But when i save it, the map boundaries are having some white pixels all along the map boundaries of map.
I really dont know why has happened to it, but cant save it in Png-8, png-24 formate due to size constraint.
Any meaningful answer will be highly appreciate and thanks in advance.
Is your background a non-changable color? Maybe you can save the image with the same color as a background.
The problem is gifs don't support true transparency.
If this doesn't work can you provide the image you are trying to save (gif and png, I don't have AI right now)? Maybe there will be something I can do about the size or clearing the gif's edges.
transparent GIFs don't have an 8-bit alpha channel, like PNG does: a pixel in a GIF is either there, or it's not: if it's there, you can't see through it. This often means that an edge between transparent and non-transparent areas looks blocky.
There are two ways to deal with this... either use a PNG 24 (and the Illustrator Save for Web feature will help you to make it smaller), or in Illustrator create a background color layer behind your image before you export to GIF. If this background color layer is the same as the website you put the image on, the edges will blend nicely.