TextRenderer is based on GDI and Graphics.DrawString is based on GDI+.Which of these functions can deliver better quality text while drawing text on an image.
i'm going to cross-post my answer from over here, just so that the information gets around.
There are two ways of drawing text in .NET:
graphics.MeasureString
and graphics.DrawString
)TextRenderer.MeasureText
and TextRenderer.DrawText
)In .NET 1.1 everything used GDI+ for text rendering. But there were some problems:
- There are some performance issues caused by the somewhat stateless nature of GDI+, where device contexts would be set and then the original restored after each call.
- The shaping engines for international text have been updated many times for Windows/Uniscribe and for Avalon (Windows Presentation Foundation), but have not been updated for GDI+, which causes international rendering support for new languages to not have the same level of quality.
So they knew they wanted to change the .NET framework to stop using GDI+'s text rendering system, and use GDI. At first they hoped they could simply change:
graphics.DrawString
to call the old DrawText
API instead of GDI+. But they couldn't make the text-wrapping and spacing match exactly as what GDI+ did.
In Windows Forms 2.0, we added support for drawing GDI text. At first we had grandiose plans of poking and prodding at the DrawText API such that we could make it match up exactly how GDI+'s DrawString API works. I actually think we got pretty close, but there are fundamental differences in word wrapping and character spacing that as mere consumers of the both APIs, Windows Forms could not solve.
So now we're presented with a problem: we want to switch everyone over to the new TextRenderer APIs so text will look better, localize better, draw more consistently with other dialogs in the operating system... ...but we dont want to break folks counting on GDI+ measure string for calculations of where their text should line up.
So they were forced to keep graphics.DrawString
to call GDI+ (compatiblity reasons; people who were calling graphics.DrawString
would suddenly find that their text didn't wrap the way it used to). From MSDN:
The GDI based TextRenderer class was introduced in the .NET Framework 2.0 to improve performance, make text look better, and improve support for international fonts. In earlier versions of the .NET Framework, the GDI+ based Graphics class was used to perform all text rendering. GDI calculates character spacing and word wrapping differently from GDI+. In a Windows Forms application that uses the Graphics class to render text, this could cause the text for controls that use TextRenderer to appear different from the other text in the application. To resolve this incompatibility, you can set the
UseCompatibleTextRendering
property to true for a specific control. To setUseCompatibleTextRendering
to true for all supported controls in the application, call the Application.SetCompatibleTextRenderingDefault method with a parameter of true.
A new static TextRenderer
class was created to wrap GDI text rendering. It has two methods:
TextRenderer.MeasureText
TextRenderer.DrawText
Note:
TextRenderer
is a wrapper around GDI, whilegraphics.DrawString
is still a wrapper around GDI+.
Then there was the issue of what to do with all the existing .NET controls, e.g.:
Label
Button
TextBox
They wanted to switch them over to use TextRenderer
(i.e. GDI), but they had to be careful. There might be people who depended on their controls drawing like they did in .NET 1.1. And so was born "compatible text rendering".
By default controls in application behave like they did in .NET 1.1 (they are "compatible").
You turn off compatibility mode by calling:
Application.SetCompatibleTextRenderingDefault(false);
This makes your application better, faster, with better international support. To sum up:
SetCompatibleTextRenderingDefault(true) SetCompatibleTextRenderingDefault(false)
======================================= ========================================
default opt-in
bad good
the one we don't want to use the one we want to use
uses GDI+ for text rendering uses GDI for text rendering
graphics.MeasureString TextRenderer.MeasureText
graphics.DrawString TextRenderer.DrawText
Behaves same as 1.1 Behaves *similar* to 1.1
Looks better
Localizes better
Faster
It's also useful to note the mapping between GDI+ TextRenderingHint
and the corresponding LOGFONT
Quality used for GDI font drawing:
TextRenderingHint mapped by TextRenderer to LOGFONT quality
======================== =========================================================
ClearTypeGridFit CLEARTYPE_QUALITY (5) (Windows XP: CLEARTYPE_NATURAL (6))
AntiAliasGridFit ANTIALIASED_QUALITY (4)
AntiAlias ANTIALIASED_QUALITY (4)
SingleBitPerPixelGridFit PROOF_QUALITY (2)
SingleBitPerPixel DRAFT_QUALITY (1)
else (e.g.SystemDefault) DEFAULT_QUALITY (0)
Here's some comparisons of GDI+ (graphics.DrawString) verses GDI (TextRenderer.DrawText) text rendering:
GDI+: TextRenderingHintClearTypeGridFit
, GDI: CLEARTYPE_QUALITY
:
GDI+: TextRenderingHintAntiAlias
, GDI: ANTIALIASED_QUALITY
:
GDI+: TextRenderingHintAntiAliasGridFit
, GDI: not supported, uses ANTIALIASED_QUALITY:
GDI+: TextRenderingHintSingleBitPerPixelGridFit
, GDI: PROOF_QUALITY
:
GDI+: TextRenderingHintSingleBitPerPixel
, GDI: DRAFT_QUALITY
:
i find it odd that DRAFT_QUALITY
is identical to PROOF_QUALITY
, which is identical to CLEARTYPE_QUALITY
.
See also