Effects of line output in different ing Modes

During print preview: it is interesting.

1: The line with the width set to 1mm is the same as the line with the width set to 2mm.
The printer output is normal.
2: print preview: some lines of the same width are not displayed.
The printer output is normal.

A closer look is actually a display problem in the ing mode. Given that the ing mode is always a focal point
It is worth summarizing:

Start analysis:
Step 1: Write an example of the MM_TEXT mode. Print 6 vertical lines with the width increasing from 1.
Dc. SetMapMode (MM_TEXT );
For (int ii = 1; ii <= 6; ii ++)
{
CPen pen;
Pen. CreatePen (PS_SOLID, ii, RGB (255, 0 ));
CPen * pOldPen = dc. SelectObject (& pen );
Dc. MoveTo (xStart + xInterval * ii, 0 );
Dc. LineTo (xStart + xInterval * ii, xLineLen );
Dc. SelectObject (& pOldPen );
}
Of course, six lines of different widths are output.
Normal. The ing mode is measured in pixels.

Step 2: Simulate the print preview mode (1mm)
Long lloginch= 254;
Dc. SetMapMode (MM_ANISOTROPIC );
Dc. SetWindowExt (lLogInch, lLogInch );
Dc. SetViewportExt (dc. GetDeviceCaps (LOGPIXELSX), dc. GetDeviceCaps (LOGPIXELSY ));
Ing: 1 unit is 0.1mm.
Also use the above Code output.
Hey: Lines 1, 2, and 3 are as thick as 4, 5, and 6.
The actual printer output, the thickness is increasing, very normal.
Why?

Step 3: Is estimation accuracy a problem?
Look at the actual output pixels of each line in the new ing mode.
First, use long lX = dc. GetDeviceCaps (LOGPIXELSX );
Obtain the current display. An inch is equal to 96 pixels.
To calculate:
0.1mm -- "96/254 = 0.378
0.2mm -- "0.756
0.3mm -- "1.134
0.4mm -- "1.512
0.5mm -- "1.89
0.6mm -- "2.268

Well, after rounding, 1, 2, 3 are all 1 pixel, 4, 5, and 6 are both 2 pixels.
What about the actual printer? LX = 600.
You don't need to calculate it. The accuracy is high. Of course, it's okay to print it out.

Conclusion 1:
Due to the pixel precision problem of the display, when you use a Pen to draw, it will be rounded. If
The current ing mode is not suitable. Different inputs on the application end are displayed in the same way after rounding.
Solution: for example, in Excel, do not provide a small line width. For example, the minimum line width must be converted.
One pixel. For example: 1/0. 378 = 0.26.

Step 4: The above rules apply only to the Line drawing method of the Pen. You can also use FillRect or
FillSolidRect mode. In addition, the starting Image 2 is displayed.
Next, try FillSolidRect:

Long xStart = 100;
Long xLineLen = 100*10;
Long xInterval = 50;
For (int ii = 0; ii <= 5; ii ++)
{
CRect rc (xStart + xInterval * ii, 0, xStart + xInterval * ii + 1, xLineLen );
Dc. FillSolidRect (rc, RGB (255, 0, 0 ));
}
Result:
Only the last four lines are displayed.
Why? Why is it not rounded up?

Step 5: The rectangle may be rounded in and then calculated in width? Yes? Do a test first.
When printing, add one more line for testing:
TRACE (_ T ("% f, % f"), rc. left * 0.378, rc. right * 0.378 );
The output is as follows:
37.800000, 38.178000
56.700000, 57.456000
75.600000, 76.734000
94.500000, 96.012000
113.400000, 115.290000
132.300000, 134.568000
Suppose that the width is:
0 0 1 1 2 3
Compare the output results.