I am willing to display a non-ASCII character in Adafruit SSD1306. The corresponding character set is in Unicode. Their library does not show where actually the mapping between ASCII & pixel drawing is done. If it was there, I'd've written code to display the characters that I need.
The hardware library depends on Adafruit GFX library; even this library doesn't explain how the mapping is done.
So, which part of the actually maps an ASCII & pixels on display?
OR Any idea to display Unicodes directly?
OR How'd you get started if pixel by pixel configuration is needed?
I am using Arduino IDE, NodeMCU, Adafruit SSD1306 128x64 I2C monochrome LED display. The text that am trying to display is large and so, am not willing to it in BMP image way.
The mapping between ASCII & pixel drawing is done in the font files.
See:
Adafruit-GFX-Library/Fonts/
Adafruit-GFX-Library/fontconvert/
Adafruit-GFX-Library/gfxfont.h
Adafruit-GFX-Library/glcdfont.c
So maybe you can create your own characters or font to display what you need.
I am developing an image processing software that extracts/crops and enhances this cropped single page form from an image taken from a cellphone camera.The form has no rectangular boundaries to simplify the process of extraction.Yes it is a white background black text format but nothing apart from that is fixed.Now some Text will be present which will verify that the image is of the form required.So my questions are these.
1) Can i search for a specific regular expression using leptonica library itself or do i have to shift focus to other libraries like the tessarect API to do this.So far i have not found anything of this sort
2) Now suppose i know the text at the top left corner and the bottom right corner and i search it succesfully.Can i get the co-ordinates of the particular text that i am searching and then crop the image accordingly?
Leptonica doesn't do anything with text, it's an image processing library.
To enable acquiring position of the text, add tessedit_create_hocr 1 to you Tesseract config file (or set this option whichever way you configure Tesseract if you're using it as a library).
The result is no longer a text file, but a UTF-8-encoded HTML file (note: it's not valid XML). Its format is self-explanatory. It will contain positions and dimensions of all words on all pages in pixels, as found on the input image. You need to parse that HTML, find the words you're looking for, and then get bounding boxed of those words.
I am drawing text in a PDF page using iTextSharp, and I have two requirements:
1) the text needs to be searchable by Adobe Reader and such
2) I need character-level control over where the text is drawn.
I can draw the text word-by-word using PdfContentByte.ShowText(), but I don't have control over where each character is drawn.
I can draw the text character-by-character using PdfContentByte.ShowText() but then it isn't searchable.
I'm now trying to create a PdfTextArray, which would seem to satisfy both of my requirements, but I'm having trouble calculating the correct offsets.
So my first question is: do you agree that PdfTextArray is what I need to do, in order to satisfy both of my original requirements?
If so, I have the PdfTextArray working correctly (in that it's outputting text) but I can't figure out how to accurately calculate the positioning offset that needs to get put between each pair of characters (right now I'm just using the fixed value -200 just to prove that the function works).
I believe the positioning offset is the distance from the right edge of the previous character to the left edge of the new character, expressed in "thousandths of a unit of text space". That leaves me two problems:
1) How wide is the previous character (in points), as drawn in the specified font & height? (I know where its left edge is, since I drew it there)
2) How do I convert from points to "units of text space"?
I'm not doing any fancy scaling or rotating, so my transformation matrices should all be identity matrices, which should simplify the calculations ...
Thanks,
Chris
I need your advise. It's about this app:
LEDit Free
EDIT: The referenced app displays text in the way a lighted board would, as a series of illuminated dots.
Basically you can insert your text and it will be scrolled through the screen. You can try it youself, there's a light version
But how did they manage to put the individual text exactly on the image with it's circles? I think it is very labour-intensive, isn't it?
When we used to do this with real LED displays, we just used bitmaps. So for example, the character H and A could be defined (in its simplest form) as arrays of booleans:
bool[] H = { 1,0,0,0,0,1, bool[] A = { 0,0,1,1,0,0,
1,0,0,0,0,1, 0,1,0,0,1,0,
1,1,1,1,1,1, 0,1,1,1,1,0,
1,0,0,0,0,1, 1,0,0,0,0,1,
1,0,0,0,0,1 } 1,0,0,0,0,1 }
Then for each character in the text it finds the right bitmap in the table and turns on the right LEDs, or in this case it switches the right images.
While I suspect they probably use the mechanism #Sietse van der Molen suggests (since it is very straightforward), there are other, more general ways to do this.
One way is to create a small black-and-white bitmap image with the resolution of your light board. Then you draw your text using whatever font you like and read the bitmap to determine which pixels are turned on.
Simple question - how is text-zooming implemented on an Android/iPhone device? Do they pre-compute frequently used bitmaps of a font and replace the text as the scale changes? Or do they extract the contours from the font files and render the text as vector graphics?
Text rendering is a fairly complex subject so any answer here will just be glossing over a lot of stuff. Typefaces are generally stored in vector format, and not bitmaps. The system lays out the text by computing the metrics of each letter and creates a vector shape that is rendered into a bitmap that is displayed on the screen. It's unlikely that the system will cache the individual letterforms as bitmaps because of the way antialiasing and subpixel rendering works. But at some point all vector graphics are converted into bitmaps because the typical computer display is made up of pixels.