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.
Related
Is there any downside to using Graphics.DrawString to render a (rather static) bunch of text to an offscreen bitmap, convert it to a Texture2D once, and then simply call SpriteBatch.Draw, instead of using the content pipeline and rendering text using SpriteFont? This is basically a page of text, drawn to a "sheet of paper", but user can also choose to resize fonts, so this means I would have to include spritefonts of different sizes.
Since this is a Windows only app (not planning to port it), I will have access to all fonts like in a plain old WinForms app, and I believe rendering quality will be much better when using Graphics.DrawString (or even TextRenderer) than using sprite fonts.
Also, it seems performance might be better since SpriteBatch.DrawString needs to "render" the entire text in each iteration (i.e. send vertices for each letter separately), while by using a bitmap I only do it once, so it should be slightly less work at the CPU side.
Are there any problems or downsides I am not seeing here?
Is it possible to get alpha blended text using spritefonts? I've seen Nuclex framework mentioned around, but it's not been ported to Monogame AFAIK.
[Update]
From the technical side, it seems to be working perfectly, much better text rendering than through sprite fonts. If they are rendered horizontally, I even get ClearType. One problem that might exist is that spritesheets for fonts are (might be?) more efficient in terms of texture memory than creating a separate texture for a page of text.
No
There doesn't seem to be any downside
In fact you seem to be following a standard approach to text rendering.
Rendering text 'properly' is a comparatively slow processed compared to rendering a textured quad, even though SpriteFonts cutout all the splining glyphs, if you are rendering a page of text then you can still be racking up a large number of triangles.
Whenever I've been looking at different text rendering solutions for GL/XNA, people tend to recommend your approach. Draw your wall of text once to a reusable texture, then render that texture.
You may also want to consider RenderTarget2D as possible solution that is portable.
As an example:
// Render the new text on the texture
LoadPageText(int pageNum) {
string[] text = this.book[pageNum];
GraphicsDevice.SetRenderTarget(pageTarget);
// TODO: draw page background
this.spriteBatchCache.Begin();
for (int i = 0; i < text.Length; i++) {
this.spriteBatchCache.DrawText(this.font,
new Vector2(10, 10 + this.fontHeight * i),
text[i],
this.color);
}
this.spriteBatchCache.End();
GraphicsDevice.SetRenderTarget(null);
}
Then in the scene render, you can spriteBatch.Draw(..., pageTarget, ...) to render the text.
This way you only need 1 texture for all your pages, just remember to also redraw if your font changes.
Other things to consider is your SpriteBatches sort mode, sometimes that may impact performance when rendering many triangles.
On point 2, as I mentioned above the SpriteFonts are pre-rendered textures, this means that the transparency is baked onto their spritesheet. As such it seems the default library uses no transparency/anti-aliasing.
If you rendered them twice as large and White on Black and used the SourceColor as an alpha channel then rendered them scaled back down blending with Color.Black you could possible get it back.
Please try color mixing with pointer:
MixedColor = ((Alpha1 * Channel1) + (Alpha2 * Channel2))/(Alpha1 + Alpha2)
I have a question regarding Cairo codings (http://cairographics.org/).
I have a filled rectangle (cairo_fill (cr)), how can I cut a hole in the middle of it representing for example the letter "S"?
So basically, I want to "engrave" text in that rectangle but also making the text transparent (like cutting a hole in the rectangle).
Anyone have any tips?
Set the fill rule to even-odd and use cairo_text_path() to get the shape of the letter "S", then cairo_fill() as you do now.
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 to render rich text using Core Text in my view (simple formatting, multiple fonts in one line of texts, etc.). I am wondering if text rendered this way can be selected by user using (standard copy / paste function)?
I implemented a text selection in CoreText. It is really a hard work... But it's doable.
Basically you have to save all CTLine rects and origins using CTFrameGetLineOrigins(1), CTLineGetTypographicBounds(2), CTLineGetStringRange(3) and CTLineGetOffsetForStringIndex(4).
The line rect can be calculated using the origin(1), ascent(2), descent(2) and offset(3)(4) as shown bellow.
lineRect = CGRectMake(origin.x + offset,
origin.y - descent,
offset,
ascent + descent);
After doing that, you can test which line has the touched point looping the lines (always remember that CoreText uses inverse Y coordinates).
Knowing the line that has the touched point, you can know the letter that is located at that point (or the nearest letter) using CTLineGetStringIndexForPosition.
Here's one screenshot.
For that loupe, I used the code shown in this post.
Edit:
To draw the blue background selection, you have to paint the rect using CGContextFillRect. Unfortunately, there's no background color in NSAttributedString.
I have a label and I wish to increase the spacing between characters.
I tried adding a space between each character, but this was too much
Perhaps there is a font with large spacing between the letters?
If all else fails, I am considering putting each character (only a size character code), into its own textbox.
Any ideas on how to achieve this?
There is a way to insert a half space, but I don't recall the exact command (option-spacebar?). Wikipedia has a complete list of spaces you can use.
Another approach would be a UIWebView with the letter-spacing CSS attribute set.
You're better off creating a custom view and using your drawRect routine to draw the text manually. You can use CFAttributedString to hold your text along with kerning information.
Update: sounds like you can't actually use CFAttributedString to draw text on the iPhone. You can still use your drawRect to draw the customized text, but it will take some more work to actually get your custom kerning to work.