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Im 15 and a newbie trying to learn more about image storage. I wrote a script in python to create a bitmap image without any imports. Im familiar with PIL/PILLOW, im not using any imports simply to learn more, as they will not help explain images at a binary level. my issue is that when i try to draw to the image, it gets distorted. For example, the code I've attached should draw out straight rows of black and white lines, but on the image it generates (attached as a png as SO won't attach a .bmp), there are fault lines where the image goes askew.
#The header contains all the metadata of the file, so that it can be scanned and displayed correctly.
#I've attached details of this header to my question
header=[b'\x42',b'\x4d',b'\x18',b'\x31',b'\x0c',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x36',b'\x00',b'\x00',b'\x00',b'\x28',b'\x00',b'\x00',b'\x00',b'\x80',b'\x02',b'\x00',b'\x00',b'\xaa',b'\x01',b'\x00',b'\x00',b'\x01',b'\x00',b'\x18',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00',b'\x00']
#create a file to write the image to, in biinary.
#you may wish to change the file path
with open ("test.bmp","wb") as f:
#first write in the header
for i in range(len(header)):
f.write(header[i])
#now write in the pixel data
#640 is the image width
for x in range(0,640):
#426 is the image height
for y in range(0,426):
#if the row is an even number, make it a white pixel.
if x %2 ==0:
byte_arr=[255,255,255]
#else make it a black pixel.
else:
byte_arr=[0,0,0]
#write the pixel data bytes to the file
some_bytes = bytearray(byte_arr)
immutable_bytes = bytes(some_bytes)
f.write(immutable_bytes)
this article has been very helpful in clearly explaining the bitmap format.
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I have been able to change the number of fault lines by changing the number of rows, but i cannot get rid of them entirely. I suspect the problem is in the files meta-data, but ive checked through it and cannot find any bad data. I've attached a (slightly messy) breakdown of the header ive used, which the article also explains in more detail.
I have a 13 column xlsx and I want convert to pdf.
I use this code: "soffice" ,"--headless","--convert-to", "pdf" , filepath ,"--outdir",outpath.
I can convert to pdf but the columns too many so they have been showed on four pages.
I need they show on one page.
And it show on straight , I need it show on horizontal.
Thanks
XLSX printout settings (PDF export) are part of the file contents so here is the same file saved with different settings but same export command. (convert-to implies headless, so not generally needed. The author decides a cell content and shape and also sets how many rows and columns will fit in a standard page such as A4 portrait or A4 Landscape etc. Thus only a macro can change print layout area. The best that may be possible externally is to scale it up or down on to bigger or smaller paper.
soffice --convert-to pdf:calc_pdf_Export "DataTables example Default.xlsx"
soffice --convert-to pdf:calc_pdf_Export "DataTables example A3.xlsx"
You need to change layout for printing and export in the preview screen if you want 13 columns you set area from A:1 to M:Y where Y is your desired number of lines (whatever their variable height may be.)
I want to extract images from PDFs retaining a knowledge of their content (page_number and coordinates on page). (Some tools (e.g. pdfminer) only emit image files with non-semantic names, e.g. Img0.bmp). I can do this with PDFBox (Java) but I'd ideally like a Python tool
My current (arbitrary) designs is to create filenames of the form:
image_<page>_<serial_in_page>_<x1>_<x2>__<y1>_<y2>.png
Currently pdfplumber exposes cooordinates but with a PDFStream and encoding information rather than an image. Code to convert the stream to a *.png would solve the problem.
(NOTE: the pdfplumber approach of rendering to the screen and capturing the known rectangle (which I use) is not a solution as the image is often degraded and frequently overwritten with text.)
(NOTE: I have had problems with several Python tools (pdfminer.six, PuMuPDF) extracting images as they make the background black which obscures black text, etc. PDFBox (Java) doesn't have this problem.)
Python tools are likely to have similar problems to any tools even those that require a single line to manipulate images or extract their details.
Here we can see a visual layout of all the compressed images in the file by using one command line to extract images. Here the individual object references have been converted into normal tiff or jpg (other tools may use pbm and pgm especially for OCR but the result is generally similar). The Greyscale Alpha softmask (B&W) transparency components are not necessarily tied direct to a page or an image other than by internal references, and usually appear like negatives.
What you may note is that the objects that were inserted most likely as one PNG are broken in two when injected into the PDF and their scaled placement is defined. Note that a raw PNG (whatever its source common resolution was) will retain number of dots but its scale when inserted into the PDF could be totally different horizontal and vertical, thus the only meaningful data is W x H in pixel values.
It is not trivial to overlay the mask on the RGB component when simply extracted but can allow for colour changes if desired.
So PDFbox is one of the simpler/better tools for blending to a suitable output, (as you have discovered) but for Python it is generally the top end library products that can identify the placement of the two images and combine into a suitable alpha output like a new PNG.
For many suggestions see Extract images from PDF without resampling, in python?.
Your related part question was knowing where those components are placed on each page since one image (and its alpha mask) could be placed multiple times such as a heading logo on each page. Again it is easy in a single command line to see which pages are referenced by a group of images, but to see which image is placed where requires analyzing each pages resources, again requiring a library interrogation of page contents, thus best done via power house libraries such as iText or any other like PDFtron for python.
For a related command in PyMuPDF see https://pymupdf.readthedocs.io/en/latest/page.html#Page.get_image_rects
I don't have a solution in Python but here is a small script using Ruby and HexaPDF:
require 'hexapdf'
class ImageBorderProcessor < HexaPDF::Content::Processor
def initialize(page, index)
super()
#page = page
#index = index
#count = 0
end
def paint_xobject(name)
super
xobject = resources.xobject(name)
return unless xobject[:Subtype] == :Image
w, h = xobject.width, xobject.height
llx, lly = graphics_state.ctm.evaluate(0, 0)
lrx, lry = graphics_state.ctm.evaluate(1, 0)
urx, ury = graphics_state.ctm.evaluate(1, 1)
ulx, uly = graphics_state.ctm.evaluate(0, 1)
# If the image is rotated, you will need all 4 coordinates, nut just the 2
filename = "image_#{#index}_#{#count}_#{llx}_#{urx}_#{lly}_#{ury}"
xobject.write(filename) rescue puts "Can write image #{#index}-#{#count}"
#count += 1
end
end
doc = HexaPDF::Document.open(ARGV[0])
doc.pages.each_with_index do |page, index|
processor = ImageBorderProcessor.new(page, index)
page.process_contents(processor)
end
It will iterate over all pages of the input document provided on the command line and create files using your file naming scheme. Since HexaPDF doesn't currently support writing all types of PDF images, you might get some error messages for those that can't be written.
If a supported image has an associated image mask defined, it will automatically be used to create a transparent image.
The script will output all images found, even repeated ones. This could easily be changed so that just a soft link is created for repeated images.
I would like send ZPL instructions to a Zebra printer (GK420t for now).
I'm printing 50mm x 20mm labels.
I would like a logo (small ~ 5mm x 5mm image) to be printed on the upper left corner of the label.
I would like to know the steps I should follow to do this.
I have been reading and trying a few things from the ZPL manual but I don't really understand how it works and couldn't find a working example.
It looks like I have to "load" the image into the printer first (in a so-called "storage area"/DRAM?) and then print it.
The .GRF file extension is mentioned many times in the manual.
I couldn't find the tool to convert a .PNG or .BMP image into a .GRF file.
I read that a .GRF file is an ASCII HEX representation of a graphic image... but it didn't help me do the work.
I could print the logo on the labels using the "Zebra Setup Utilities", by "Downloading Fonts and Graphics", choosing any available .MMF file, adding a .BMP picture, downloading it [to the printer] and printing a test page.
But until now, I couldn't do it using ZPL instructions.
I am also wondering what are the best dimensions I should use given the fact that I need a small image ~5mm x 5mm to be printed on the labels.
The image I printed is a 40px x 40px image.
Also, if I have to make a .GRF file from an original image what should be the type of this file (.BMP, .PNG, .JPG)?
Can you advise me how to proceed?
It sounds like you have some existing ZPL code, and all you want to do is add an image to it.
If that's the case, the easiest solution is probably to go to the Labelary online ZPL viewer, paste your ZPL into the viewer, click "Add image", and upload the image that you want to add to the ZPL.
This should modify your ZPL by adding the image ZPL commands that you need, and you can then tweak the position, etc.
Here is another option: I created my own image to .GRF converter in python. Feel free to use it.
from PIL import Image, ImageOps
import re
import itertools
import numpy as np
# Use: https://www.geeksforgeeks.org/round-to-next-greater-multiple-of-8/
def RoundUp(x, multiple_of = 8):
return ((x + 7) & (-1 * multiple_of))
def image2grf(filePath, width = None, height = None, rotate = None):
image = Image.open(filePath).convert(mode = "1")
#Resize image to desired size
if (width != None):
size = (width, height or width)
if (isinstance(size[0], float)):
size = (int(size[0] * image.width), int(size[1] * image.height))
#Size must be a multiple of 8
size = (RoundUp(size[0]), RoundUp(size[1]))
# image.thumbnail(size, Image.ANTIALIAS)
image = image.resize(size)
if (rotate != None):
image = image.rotate(rotate, expand = True)
image_asArray = np.asarray(np.asarray(image, dtype = 'int'), dtype = 'str').tolist()
bytesPerRow = len(image_asArray[0])
nibblesPerRow = bytesPerRow // 4
totalBytes = nibblesPerRow * len(image_asArray)
#Convert image to hex string
hexString = "".join(
format(int("".join(row[i*4:i*4 + 4]), 2) ^ 0xF, "x")
for row in image_asArray
for i in range(nibblesPerRow)
)
#Compose data
data = "~DGimage," + str(totalBytes // 2) + "," + str(nibblesPerRow // 2) + "," + hexString
#Save image
fileHandle = open(r"labelPicture.grf", "w")
fileHandle.write(data)
fileHandle.close()
if __name__ == '__main__':
# image2grf(r"warning.bmp")
image2grf(r"pallet_label_icons.png", rotate = 90)
Edit: I updated the code above to use my new conversion method, which produces better resolution GRF files
Just install ZebraDesigner, create a blank label, insert a image object to the template and add the required logo image.
Print to File this label (a *.prn file) and open the recently created file with Notepad++ (MS Notepad will ruin the data if opened and saved with). Find a huge string of seemingly random characters, and there is your image's data. Careful not to lose any of those characters, including the control ones, as the whole string is a textual representation of your image (as it would be if it were base64).
Tip0: Always have your ZPLII Programmer's Guide at hand, you'll need/want to check if ZebraDesigner sent the image to memory or directly to the printer buffer.
Tip1: Before adding the logo to the label and get the text, prepare the image making it greyscale (remember to check the printer's dithering configuration!) or, in my case, plain black and white (best result IMHO). The image can be colored, the ZebraDesigner will make it work for the printer converting the image to greyscale before conversion to commands and text.
I created a PHP script to convert PNG images to .GRF similar to Josh Mayberry's image2grf.py:
https://gist.github.com/thomascube/9651d6fa916124a9c52cb0d4262f2c3f
It uses PHP's GD image function and therefore can work with all the file formats GD can open. With small modifications, the Imagick extension could be used but performance seems to be better with GD.
Try codeproject's sharpzebra project. The test program that is part of project prints a graphic and I know this works at least it did on a ZM400
go to Object ==> Picture and your curser will change to something else.. when it changed go and click on the working area and a dialog box iwll apear... so on there select the image so you can see the image whant you wanna print on the printer i am using GT800 so for me i did like that hope this will helps you
Use ZebraNet Bridge Enterprise Software to convert BMP to GRF file format
I had to figure this out again today. In the ZPL code, you can output the graphic bytes for every single label (which means a lot of additional data when you're printing a few thousand labels), or you can define the image first and then refer to it.
I used an online ZPL viewer to save on the number of labels printed when testing. I used:
http://staging.advanced-technology-group.com/
and here is another that does the same:
http://labelary.com/viewer.html
These (currently) have an 'add image' function. This transfers a png to the GRF format that ZPL works with (see the other answers if you need to generate these bytes yourself).
Outputting the bytes for every label
Using the "Add image" function generates a command and the graphic bytes, which looks like:
^FO50,50^GFA,11118,11118,17,,<lots of data>
You can adjust the FO as that tells the printer where to position the graphic.
That should be fine for shorter runs / smaller pictures / you're in a hurry.
Downloading the image once and then referring
This is what I had to do, so I needed to rearrange the bytes a bit (nice pun?).
THe ^GF command stands for Graphic Field: ^GFa,b,c,d,data where
a: A|B (A, non-binary, B = binary)
b: number of bytes transmitted
c: number of bytes comprising the graphic format
d: number of bytes per row
and what I needed to do is to reformat this as ~DGR:000.GRF,11118,17,, so that I could refer to it with ^XGR:000.GRF,1,1. After the print run, I'd need to delete the graphic from memory again with: ^ID000.GRF
The properties for ~DGd:o.x,t,w,data mean
d: memory destination - R for RAM
o: image name (1-8 alphanumeric chars)
x: filename extension, always GRF
t: number of bytes in the graphic
w: number of bytes per row
So I turned:
^FO50,50^GFA,11118,11118,17,,<data>
into:
~DGR:000.GRF,11118,17,,<data>
This definition goes before the label-definition, so:
~DGR:000.GRF,11118,17,,<data>
^XA (start of label)
...
^FT360,700^XGR:000.GRF,1,1^FS <-- this outputs the graphic
...
^XZ (end of label)
^ID000.GRF
I'm currently creating my figures in matlab to embed themvia latex into a pdf for later printing. I save the figures and save them via the script export_fig! Now I wonder which is the best way to go:
Which size of the matlab figure window to chose
Which -m option to take for the script? It will change the resolution and the size of the image...
I'm wondering about those points in regards to the following two points:
When chosing the figure-size bigger, there are more tickmarks shown and the single point markers are better visible
When using a small figure and using a big -m option, I still have only some tickmarks
When I generate a image which is quite huge (e.g. resolution 300 and still 2000*2000px) and than embed it into the document: Does this than look ugly? Will this be embedded in a nice scaling mode or is it the same ugliness as if you upload a 1000*1000px image onto a homepage and embed it via the widht and height tags in html -> the browser displays it quite ugly because the browser doesn't do a real resize. So it looks unsharp and ugly.
Thanks in advance!
The MATLAB plots are internally described as vector graphics, and PDF files are also described using vector graphics. Rendering the plot to a raster format is a bad idea, because you end up having to choose resolution and end up with bigger files.
Just save the plot to EPS format, which can be directly embedded into a PDF file using latex. I usually save my MATLAB plots for publication using:
saveas(gcf, 'plot.eps', 'epsc');
and embed them directly into my latex file using:
\includegraphics[width=0.7\linewidth]{plot.eps}
Then, you only need to choose the proportion of the line the image is to take (in this case, 70%).
Edit: IrfanView and others (XnView) don't display EPS very well. You can open them in Adobe Illustrator to get a better preview of what it looks like. I always insert my plots this way and they always look exactly the same in the PDF as in MATLAB.
One bonus you also get with EPS is that you can actually specify a font size so that the text is readable even when you resize the image in the document.
As for the number of ticks, you can look at the axes properties in the MATLAB documentation. In particular, the XTick and YTick properties are very useful manually controlling how many ticks appear no matter what the window resolution is.
Edit (again): If you render the image to a raster format (such as PNG), it is preferable to choose the exact same resolution as the one used in the document. Rendering a large image (by using a big window size) and making it small in the PDF will yield bad results mainly because the size of the text will scale directly with the size of the image. Rendering a small image will obviously make for a very bad effect because of stretching.
That is why you should use a vector image format. However, the default MATLAB settings for figures produce some of the same problems as raster images: text size is not specified as a font size and the number of ticks varies with the window size.
To produce optimal plots in the final render, follow the given steps:
Set the figure's font size to a decent setting (e.g. 11pt)
Render the plot
Decide on number of ticks to get a good effect and set the ticks manually
Render the image to color EPS
In MATLAB code, this should look somewhat like the following:
function [] = nice_figure ( render )
%
% invisible figure, good for batch renders.
f = figure('Visible', 'Off');
% make plots look nice in output PDF.
set(f, ...
'DefaultAxesFontSize', 11, ...
'DefaultAxesLineWidth', 0.7, ...
'DefaultLineLineWidth', 0.8, ...
'DefaultPatchLineWidth', 0.7);
% actual plot to render.
a = axes('Parent', f);
% show whatever it is we need to show.
render(a);
% save file.
saveas(f, 'plot.eps', 'epsc');
% collect garbarge.
close(f);
end
Then, you can draw some fancy plot using:
function [] = some_line_plot ( a )
%
% render data.
x = -3 : 0.001 : +3;
y = expm1(x) - x - x.^2;
plot(a, x, y, 'g:');
title('f(x)=e^x-1-x-x^2');
xlabel('x');
ylabel('f(x)');
% force use of 'n' ticks.
n = 5;
xlimit = get(a, 'XLim');
ylimit = get(a, 'YLim');
xticks = linspace(xlimit(1), xlimit(2), n);
yticks = linspace(ylimit(1), ylimit(2), n);
set(a, 'XTick', xticks);
set(a, 'YTick', yticks);
end
And render the final output using:
nice_figure(#some_line_plot);
With such code, you don't need to worry about the window size at all. Notice that I haven't even showed the window for you to play with its size. Using this code, I always get beautiful output and small EPS and PDF file sizes (much smaller than when using PNG).
The only thing this solution does not address is adding more ticks when the plot is made larger in the latex code, but that can't be done anyways.