I was trying to resize a pdf file to 8.5x11 with ImageMagick and in doing so, I am loosing the quality of my pdf file.
I was using convert source.pdf -extent 612x792 destination.pdf command.
Can someone please help me with this one?
Imagemagick is rasterizing the PDF, then scaling it, then producing an output PDF of differing dimensions, which contains raster data only.
Scale a PDF to fit directly like this:
cpdf -scale-to-fit "612 792" in.pdf -o out.pdf
This keeps the PDF's original vector artwork and fonts intact.
Imagemagick uses Ghostscript and will rasterize your PDF. It will not maintain its vectors. If you want higher quality, use a higher -density to rasterize and then resize back to whatever you want. For example, I use a density 4x the default of 72 or 288 and then resize by 25%=1/4 to get back to the nominal size.
convert -density 288 -units pixelsperinch image.pdf -resize 25% result.pdf
You can then include your -density 72 -gravity XX -extent 612x792 before the output.
Or you can compute do -density 288 etc and then just resize to 612x792.
I've tried this and it worked.
convert -density 300 -define pdf:fit-page=Letter -gravity Center source.pdf output.pdf
Related
I'm trying to apply watermark on an image using the following imagemagick command
convert input.png watermark.png.png -gravity northwest -composite output.png
The input png file size is 16KB and the watermark file size is 900bytes, but when I executed the above command to apply a watermark, the output png size is 61KB which is almost 4X the size of the original input png file. Is there any better way of applying a watermark to an image file with much better result in terms of output filesize
Test Image: https://res.cloudinary.com/deks86ilr/image/upload/v1533015495/1_rnpbye.png
Test watermark: https://res.cloudinary.com/deks86ilr/image/upload/v1533015494/2_usmonh.png
Here are my results of processing of your images with my PNG8 output using ImageMagick 6.9.10.8 Q16 with libpng 1.6.34.
I note that your input image was type palette, which means it is 8-bits of color per pixel and not 24-bit color. So it is already a low quality image.
Input (~16 KB):
Watermark Image (white on transparency -- so it is invisible here):
Convert to 24-bit PNG:
convert input.png watermark.png -gravity northwest -compose over -composite input_with_watermark.png
I see no significant visible quality loss but the output is now increase from 16 KB to 60 KB. But you can use tools such as pngcrush to compress it further.
Convert to 8-bit PNG:
convert input.png watermark.png -gravity northwest -compose over -composite PNG8:input_with_watermark2.png
The file size is now back to about 16 KB. But as you note the quality is a little poorer. This is likely because the input image (at 8-bits and has 217 colors) was first read back to 24-bits, then watermarked, which included new shades of white and then quantized back to 8-bits, but contains only 84 colors colors.
Another way is to add +dither -colors 256 to the command (the +dither turns off dithering):
convert 1_rnpbye.png 2_usmonh.png -gravity northwest -compose over -composite +dither -colors 256 PNG8:watermark3.png
This is a bit better, since it now uses 189 colors and still has a file size of 16 KB.
One final method is to save the colors from your input to a colortable image. Then use -remap to recolor the output using that colortable:
convert 1_rnpbye.png -unique-colors colortable.gif
convert 1_rnpbye.png 2_usmonh.png -gravity northwest -compose over -composite +dither -remap colortable.gif PNG8:watermark4.png
This results in 8-bit output with 227 colors and still a file size of about 16 KB. So it has a few more colors than your input and visually looks about the same quality as your input.
If you cannot reproduce these results, then perhaps you should upgrade either or both ImageMagick and libpng.
I have a large number of research pdf figures, and I need to preform the following actions in ImageMagick:
convert all pdf to png
crop png from left/top corner x:334/y:244; from right/bottom corner x:214/y:340;
original size 2100x2100, cropped size 1552x1552 pixels
resize cropped png to 240x240 pixels
Here is how it should be cropped for point 2, the pink area is what I want to have:
I was only be able to get 1st action done with my knowledge:
mogrify -format png -density 300 -flatten *.pdf
How can I do the 2nd and 3rd actions please? And do I need to run three separated commands or could they be combined into one command?
I do not know what exact order you need for mogrify as I do not use it. I also do not know why you need flatten Try:
mogrify -format png -density 300 -crop 1552x1552+344+244 +repage -resize 240x240 *.pdf
If the page parameter is set, conversion of PDF files at a given density outputs blank pages.
"convert -units PixelsPerInch -density 300 $myfiles -page A4 -gravity center test.pdf"
If I omit page parameter from the command, I get appropriate output but at 72dpi default resolution.
Any idea?
A4 page size is 595 x 842. So in ImageMagick you could try
convert -units PixelsPerInch -density 300 $myfiles +repage -resize 595x842 test.pdf
That will make an A4 pixel dimension image with 300 dpi. You could also do
convert -units PixelsPerInch -density 300 $myfiles +repage -resize 595x842 -density XX test.pdf
Where XX is the dpi you want when printing the image of that size.
I added +repage to remove any input image virtual canvas, since you did not specify what format images you are using for $myfiles. Without +repage, that could have caused a large bit of white space at the top of your result.
Note it is always best and most helpful to provide your ImageMagick version and platform when asking questions about its use.
While I was trying to tweak the command I found that a set density (i.e, density 300) with a given page parameter actually sets the density of the -page A4 but not the converted object on page as the set density can't actually determine resolution of the -page A4 to which it shall be applicable. As a result, the command returns blurry or blank image on set page.
However, extent parameter is what, which actually outputs the appropriate image as it is possible to set the page resolution with this parameter at a predefined density. The following example will make it absolutely clear.
Resolution of A4 size page at 300 dpi is 2480x3508, thus correct command for a set density like 300 dpi shall be:
"convert -units PixelsPerInch -density 300 $myfiles -gravity center -extent 2480x3508 test.pdf"
Resolution of A4 size page at 72 dpi is 595x842, thus correct command for a set density like 72 dpi shall be:
"convert -units PixelsPerInch -density 72 $myfiles -gravity center -extent 595x842 test.pdf"
I want to convert pdf pages to images of same size(aspect ratio maintained) irrespective of the pdf quality. Say A4 size. I am using convert from Imagemagick for this but struggling to get the fixed size of images for different pdfs of different quality.
Can anyone help me?
Something like:
convert -density 288 document.pdf -resize 2480x3508 result.png
The density must come before the PDF to ensure the rasterisation is done at sufficient quality/resolution.
If you want that centred on a piece of A4 and padded with white to fill the page:
convert -density 288 document.pdf -resize 2480x3508 -background white -gravity center -extent 2480x3508 result.png
I want to convert different image formats (bmp,jpg,gif,png,tiff-incluging multipaged) into a PDF format with A4 page size and with images fit to page (resized if necessary). Image should be positioned at the center of the page and I'd like to define an offset.
I tried the code below but there is no offset at the top and the image quality is really poor.
convert png.png -gravity North -resize 500x500 -quality 100 -page a4x5x5 myout.pdf
Is there any way to do that?
Thanks in advance for any help,
Mariusz
If you want to keep the original resolution (lossless) you can try the following command:
convert png.png -background white -page a4 myoutput.pdf
Based on a comment posted before: https://stackoverflow.com/a/24573341/6747994
#m4tx This command only makes sense if the picture has a resolution above 500x800px, it does not zoom in, to avoid pixelated thumbnails.
You can convert to pdf using ImageMagick
convert png.png myout.pdf
but use pdfjam instead of ImageMagick to adjust the page size
pdfjam --paper a4paper --outfile myoutA4.pdf myout.pdf
pdfjam offers other options, which may fit your needs.
Found this somewhere on stackoverflow:
convert *.jpg -resize 1240x1753 \
-extent 1240x1753 -gravity center \
-units PixelsPerInch -density 150x150 multipage.pdf
Thanks to the ImageMagick support forum I was able to find a solution:
convert image.tif -resize 575x823^> -gravity center -background white -extent 595x842 image.pdf
If you get an error try:
convert image.tif -resize 595x842^\> -gravity center -background white -extent 595x842 image.pdf
You need to specify the density:
convert -density 80 -page a4 input_A.jpg input_B.jpg output.pdf
Otherwise, there can be an issue when printing with "actual size" instead of "fit". I have used a public printer where I could not choose "fit" and had to choose "actual size", in which case the printed page was only a part of the page which I wanted to print.