DrawText doesn't work, but Graphics::DrawString is ok - graphics

I am creating a bitmap in the memory which combine with an image and text. My code is:
HDC hdcWindow = GetDC();
HDC hdcMemDC = CreateCompatibleDC(hdcWindow);
HBITMAP hbmDrag = NULL;
if (!hdcMemDC) {
ReleaseDC(hdcWindow);
return NULL;
}
RECT clientRect = {0};
GetClientRect(&clientRect);
hbmDrag = CreateCompatibleBitmap(hdcWindow, 256, 256);
if(hbmDrag) {
SelectObject(hdcMemDC, hbmDrag);
FillRect(hdcMemDC, &clientRect, mSelectedBkgndBrush);
Graphics graphics(hdcMemDC);
// Draw the icon
graphics.DrawImage(mImage, 100, 100, 50, 50);
#if 1
CRect desktopLabelRect(0, y, clientRect.right, y);
HFONT desktopFont = mNameLabel.GetFont();
HGDIOBJ oldFont = SelectObject(hdcMemDC, desktopFont);
SetTextColor(hdcMemDC, RGB(255,0,0));
DrawText(hdcMemDC, mName, -1, desktopLabelRect, DT_CENTER | DT_END_ELLIPSIS | DT_CALCRECT);
#else
// Set font
Font font(hdcMemDC, mNameLabel.GetFont());
// Set RECT
int y = DEFAULT_ICON_HEIGHT + mMargin;
RectF layoutRect(0, y, clientRect.right, y);
// Set display format
StringFormat format;
format.SetAlignment(StringAlignmentCenter);
// Set brush
SolidBrush blackBrush(Color(255, 0, 0, 0));
// Draw the label
int labelWide = DEFAULT_ICON_WIDTH + mMargin;
CString labelName = GetLayOutLabelName(hdcMemDC, labelWide, mName);
graphics.DrawString(labelName, -1, &font, layoutRect, &format, &blackBrush);
#endif
}
DeleteDC(hdcMemDC);
ReleaseDC(hdcWindow);
return hbmDrag;
The image can be outputted to the bitmap success.
For the text, if I use "DrawText", it can't be shown in the bitmap although the return value is correct;
But Graphics::DrawString can output the text success.
I don't know the reason. Anybody can pls tell me?
Thanks a lot.

You are passing the DT_CALCRECT flag to DrawText(). This flag is documented as (emphasis mine):
Determines the width and height of the rectangle. If there are
multiple lines of text, DrawText uses the width of the rectangle
pointed to by the lpRect parameter and extends the base of the
rectangle to bound the last line of text. If the largest word is wider
than the rectangle, the width is expanded. If the text is less than
the width of the rectangle, the width is reduced. If there is only one
line of text, DrawText modifies the right side of the rectangle so
that it bounds the last character in the line. In either case,
DrawText returns the height of the formatted text but does not draw
the text.

Related

How can I wait for a Particular Pixel's Color to Load?

I am using Win32Api(Windows API) with C/C++.
I am able to take the pixel's RGB color.
void WaitForSinglePixel(int x, int y,COLORREF color) //Passing pixel's (X,Y) co-ordinate & the particular Color I need at that pixel.
{
COLORREF _tempcolor; //in _tempcolor I will assign current color of the pixel at (x,y)
DWORD Red = GetRValue(color); DWORD Green = GetGValue(color); DWORD Blue = GetBValue(color);
do //Creating a busy loop
{
HDC dc = GetDC(NULL);
_tempcolor = GetPixel(dc, x, y); //assigning current color of the pixel at (x,y)
ReleaseDC(NULL, dc);
} while( (GetRValue(_tempcolor) != Red) & (GetGValue(_tempcolor) != Green) & (GetBValue(_tempcolor) != Blue) );
}
But I don't want to make a busy loop. Is there any method or any way to Wait For A Pixel's particular color to load without using busy loop??
There is no API that allows you to register a callback to be called whenever a pixel's color changes.

HTML5 Canvas: Rendering aliased text

When you render text on an HTML5 canvas (using the fillText command, for example), the text will render anti-aliased, meaning the text looks smoother. The downside is that it becomes very noticable when trying to render small text or specifically non-aliased fonts (such as Terminal). Because of this, what I want to do is render text aliased, rather than anti-aliased.
Is there any way to do so?
Unfortunately, there is no native way to turn off anti-aliasing for text.
The solution is to use the old-school approach of bitmap fonts, that is, in the case of HTML5 canvas a sprite-sheet where you copy each bitmap letter to the canvas. By using a sprite-sheet with transparent background you can easily change the color/gradient etc. of it as well.
An example of such bitmap:
For it to work you need to know what characters it contains ("map"), the width and height of each character, and the width of the font bitmap.
Note: In most cases you'll probably end up with a mono-spaced font where all cells have the same size. You can use a proportional font but in that case you need to be aware of that you need to map each character with an absolute position and include the width and height as well for its cell.
An example with comments:
const ctx = c.getContext("2d"), font = new Image;
font.onload = () => {
// define some meta-data
const charWidth = 12; // character cell, in pixels
const charHeight = 16;
const sheetWidth = (font.width / charWidth)|0; // width, in characters, of the image itself
// map so we can use index of a char. to calc. position in bitmap
const charMap = " !\"#$% '()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~§";
// Draw some demo text
const timeStart = performance.now();
fillBitmapText(font, "Demo text using bitmap font!", 20, 20);
fillBitmapText(font, "This is line 2...", 20, 45);
const timeEnd = performance.now();
console.log("Text above rendered in", timeEnd - timeStart, "ms");
// main example function
function fillBitmapText(font, text, x, y) {
// always make sure x and y are integer positions
x = x|0;
y = y|0;
// current x position
let cx = x;
// now, iterate over text per char.
for(let char of text) {
// get index in map:
const i = charMap.indexOf(char);
if (i >= 0) { // valid char
// Use index to calculate position in bitmap:
const bx = (i % sheetWidth) * charWidth;
const by = ((i / sheetWidth)|0) * charHeight;
// draw in character on canvas
ctx.drawImage(font,
// position and size from font bitmap
bx, by, charWidth, charHeight,
// position on canvas, same size
cx, y, charWidth, charHeight);
}
cx += charWidth; // increment current canvas x position
}
}
}
font.src = "//i.stack.imgur.com/GeawH.png";
body {background:#fff}
<canvas id=c width=640></canvas>
This should produce an output similar to this:
You can modify this to suit your needs. Notice that the bitmap used here is not transparent - I'll leave that to OP.

Apply color using VAO in jogl

I am trying to color my polygons in jogl. I have stored the vertices in an array, an index array for the triangle order and a color array. The code is as follows, but the problem that I am facing is that the triangle are white, and not the color from the color buffer.
float f[] = {1000,2000,-4000,-2000,-2000,-4000,2000,-2000,-4000,1000,-4000,-4000};
FloatBuffer buffer = GLBuffers.newDirectFloatBuffer(12);
this.coordCount = 12;
buffer.put(f);
buffer.rewind();
int indx[] = {0,1,2,1,3,2};
IntBuffer indxBuffer = GLBuffers.newDirectIntBuffer(6); //Total number of vertices
this.indexCount = 6;
indxBuffer.put(indx);
indxBuffer.rewind();
float color[] = {1,0,1,0,0,0,0,0,0,1,0,0};
FloatBuffer colorBuffer = GLBuffers.newDirectFloatBuffer(12);
colorBuffer.put(color);
colorBuffer.rewind();
gl.glDisable(GL.GL_TEXTURE_2D);
gl.glEnableClientState(GLPointerFunc.GL_COLOR_ARRAY);
gl.glEnableClientState(GLPointerFunc.GL_VERTEX_ARRAY);
gl.glFrontFace(GL.GL_CCW);
gl.glVertexPointer(3, GL.GL_FLOAT, 0, buffer);
gl.glColorPointer(3, GL.GL_FLOAT, 0, colorBuffer);
gl.glDrawElements(GL.GL_TRIANGLES, this.indexCount, GL.GL_UNSIGNED_INT, indxBuffer);
gl.glDisableClientState(GLPointerFunc.GL_COLOR_ARRAY);
gl.glDisableClientState(GLPointerFunc.GL_VERTEX_ARRAY);
gl.glEnable(GL.GL_TEXTURE_2D);
I am doing this rendering on NASA world wind globe. But I don't think that should cause any problems. Can someone help me figure out the problem? I am stuck on this for a while.
Thanks,
Got the solution, Just had to enable color and material.
gl.glEnable(GL2.GL_COLOR_MATERIAL);
gl.glColorMaterial(GL2.GL_FRONT_AND_BACK, GL2.GL_DIFFUSE);

Trying to draw Rotated text with CGAffineTransform and MakeRotation appears at wrong location

I'm trying to draw some rotated texts by using the CGAffineTransform.MakeRotation method at specifc location. I also make use of the TranslateCTM, but something must be wrong as rotated texts do not appear aligned and at the correct x, y position where they should appear, here is simple the code I'm using, anyone know where the problem is? :
public override void Draw (RectangleF rect)
{
DrawTextRotated("Hello1",10,100,30);
DrawTextRotated("Hello2",50,100,60);
SetNeedsDisplay();
}
static public float DegreesToRadians(float x)
{
return (float) (Math.PI * x / 180.0);
}
public void DrawTextRotated(string text,int x, int y, int rotDegree)
{
CGContext c = UIGraphics.GetCurrentContext();
c.SaveState();
c.TextMatrix = CGAffineTransform.MakeRotation((float)DegreesToRadians((float)(-rotDegree)));
c.ConcatCTM(c.TextMatrix);
float xxx = ((float)Math.Sin(DegreesToRadians((float)rotDegree))*y);
float yyy = ((float)Math.Sin(DegreesToRadians((float)rotDegree))*x);
// Move the context back into the view
c.TranslateCTM(-xxx,yyy);
c.SetTextDrawingMode(CGTextDrawingMode.Fill);
c.SetShouldSmoothFonts(true);
MonoTouch.Foundation.NSString str = new MonoTouch.Foundation.NSString(text);
SizeF strSize = new SizeF();
strSize = str.StringSize(UIFont.SystemFontOfSize(12));
RectangleF tmpR = new RectangleF(x,y,strSize.Width,strSize.Height);
str.DrawString(tmpR,UIFont.SystemFontOfSize(12),UILineBreakMode.WordWrap,UITextAlignment.Right);
c.RestoreState();
}
Thanks !
Here's some code that will draw text rotated properly about the top-left corner of the text. For the moment, I'm disregarding your use of text alignment.
First, a utility method to draw a marker where we expect the text to show up:
public void DrawMarker(float x, float y)
{
float SZ = 20;
CGContext c = UIGraphics.GetCurrentContext();
c.BeginPath();
c.AddLines( new [] { new PointF(x-SZ,y), new PointF(x+SZ,y) });
c.AddLines( new [] { new PointF(x,y-SZ), new PointF(x,y+SZ) });
c.StrokePath();
}
And the code to draw the text (note I've replaced all int rotations with float, and you may want negate your rotation):
public void DrawTextRotated(string text, float x, float y, float rotDegree)
{
CGContext c = UIGraphics.GetCurrentContext();
c.SaveState();
DrawMarker(x,y);
// Proper rotation about a point
var m = CGAffineTransform.MakeTranslation(-x,-y);
m.Multiply( CGAffineTransform.MakeRotation(DegreesToRadians(rotDegree)));
m.Multiply( CGAffineTransform.MakeTranslation(x,y));
c.ConcatCTM( m );
// Draws text UNDER the point
// "This point represents the top-left corner of the string’s bounding box."
//http://developer.apple.com/library/ios/#documentation/UIKit/Reference/NSString_UIKit_Additions/Reference/Reference.html
NSString ns = new NSString(text);
UIFont font = UIFont.SystemFontOfSize(12);
SizeF sz = ns.StringSize(font);
RectangleF rect = new RectangleF(x,y,sz.Width,sz.Height);
ns.DrawString( rect, font);
c.RestoreState();
}
Rotation about a point requires translation of the point to the origin followed by rotation, followed by rotation back to the original point. CGContext.TextMatrix has no effect on NSString.DrawString so you can just use ConcatCTM.
The alignment and line break modes don't have any effect. Since you're using NSString.StringSize, the bounding rectangle fits the entirety of the text, snug up against the left and right edges. If you make the width of the bounding rectangle wider and use UITextAlignment.Right, you'll get proper right alignment, but the text will still rotate around the top left corner of the entire bounding rectangle. Which is not, I'm guessing, what you're expecting.
If you want the text to rotate around the top right corner, let me know and I'll adjust the code accordingly.
Here's the code I used in my test:
DrawTextRotated("Hello 0",100, 50, 0);
DrawTextRotated("Hello 30",100,100,30);
DrawTextRotated("Hello 60",100,150,60);
DrawTextRotated("Hello 90",100,200,90);
Cheers.

Rotating an Image in Silverlight without cropping

I am currently working on a simple Silverlight app that will allow people to upload an image, crop, resize and rotate it and then load it via a webservice to a CMS.
Cropping and resizing is done, however rotation is causing some problems. The image gets cropped and is off centre after the rotation.
WriteableBitmap wb = new WriteableBitmap(destWidth, destHeight);
RotateTransform rt = new RotateTransform();
rt.Angle = 90;
rt.CenterX = width/2;
rt.CenterY = height/2;
//Draw to the Writeable Bitmap
Image tempImage2 = new Image();
tempImage2.Width = width;
tempImage2.Height = height;
tempImage2.Source = rawImage;
wb.Render(tempImage2,rt);
wb.Invalidate();
rawImage = wb;
message.Text = "h:" + rawImage.PixelHeight.ToString();
message.Text += ":w:" + rawImage.PixelWidth.ToString();
//Finally set the Image back
MyImage.Source = wb;
MyImage.Width = destWidth;
MyImage.Height = destHeight;
The code above only needs to rotate by 90° at this time so I'm just setting destWidth and destHeight to the height and width of the original image.
It looks like your target image is the same size as your source image. If you want to rotate over 90 degrees, your width and height should be exchanged:
WriteableBitmap wb = new WriteableBitmap(destHeight, destWidth);
Also, if you rotate about the centre of the original image, part of it will end up outside the boundaries. You could either include some translation transforms, or simply rotate the image about a different point:
rt.CenterX = rt.CenterY = Math.Min(width / 2, height / 2);
Try it with a piece of rectangular paper to see why that makes sense.
Many thanks to those above.. they helped a lot. I include here a simple example which includes the additional transform necessary to move the rotated image back to the top left corner of the result.
int width = currentImage.PixelWidth;
int height = currentImage.PixelHeight;
int full = Math.Max(width, height);
Image tempImage2 = new Image();
tempImage2.Width = full;
tempImage2.Height = full;
tempImage2.Source = currentImage;
// New bitmap has swapped width/height
WriteableBitmap wb1 = new WriteableBitmap(height,width);
TransformGroup transformGroup = new TransformGroup();
// Rotate around centre
RotateTransform rotate = new RotateTransform();
rotate.Angle = 90;
rotate.CenterX = full/2;
rotate.CenterY = full/2;
transformGroup.Children.Add(rotate);
// and transform back to top left corner of new image
TranslateTransform translate = new TranslateTransform();
translate.X = -(full - height) / 2;
translate.Y = -(full - width) / 2;
transformGroup.Children.Add(translate);
wb1.Render(tempImage2, transformGroup);
wb1.Invalidate();
If the image isn't square you will get cropping.
I know this won't give you exactly the right result, you'll need to crop it afterwards, but it will create a bitmap big enough in each direction to take the rotated image.
//Draw to the Writeable Bitmap
Image tempImage2 = new Image();
tempImage2.Width = Math.Max(width, height);
tempImage2.Height = Math.Max(width, height);
tempImage2.Source = rawImage;
You need to calculate the scaling based on the rotation of the corners relative to the centre.
If the image is a square only one corner is needed, but for a rectangle you need to check 2 corners in order to see if a vertical or horizontal edge is overlapped. This check is a linear comparison of how much the rectangle's height and width are exceeded.
Click here for the working testbed app created for this answer (image below):
double CalculateConstraintScale(double rotation, int pixelWidth, int pixelHeight)
The pseudo-code is as follows (actual C# code at the end):
Convert rotation angle into Radians
Calculate the "radius" from the rectangle centre to a corner
Convert BR corner position to polar coordinates
Convert BL corner position to polar coordinates
Apply the rotation to both polar coordinates
Convert the new positions back to Cartesian coordinates (ABS value)
Find the largest of the 2 horizontal positions
Find the largest of the 2 vertical positions
Calculate the delta change for horizontal size
Calculate the delta change for vertical size
Return width/2 / x if horizontal change is greater
Return height/2 / y if vertical change is greater
The result is a multiplier that will scale the image down to fit the original rectangle regardless of rotation.
**Note: While it is possible to do much of the maths using matrix operations, there are not enough calculations to warrant that. I also thought it would make a better example from first-principles.*
C# Code:
/// <summary>
/// Calculate the scaling required to fit a rectangle into a rotation of that same rectangle
/// </summary>
/// <param name="rotation">Rotation in degrees</param>
/// <param name="pixelWidth">Width in pixels</param>
/// <param name="pixelHeight">Height in pixels</param>
/// <returns>A scaling value between 1 and 0</returns>
/// <remarks>Released to the public domain 2011 - David Johnston (HiTech Magic Ltd)</remarks>
private double CalculateConstraintScale(double rotation, int pixelWidth, int pixelHeight)
{
// Convert angle to radians for the math lib
double rotationRadians = rotation * PiDiv180;
// Centre is half the width and height
double width = pixelWidth / 2.0;
double height = pixelHeight / 2.0;
double radius = Math.Sqrt(width * width + height * height);
// Convert BR corner into polar coordinates
double angle = Math.Atan(height / width);
// Now create the matching BL corner in polar coordinates
double angle2 = Math.Atan(height / -width);
// Apply the rotation to the points
angle += rotationRadians;
angle2 += rotationRadians;
// Convert back to rectangular coordinate
double x = Math.Abs(radius * Math.Cos(angle));
double y = Math.Abs(radius * Math.Sin(angle));
double x2 = Math.Abs(radius * Math.Cos(angle2));
double y2 = Math.Abs(radius * Math.Sin(angle2));
// Find the largest extents in X & Y
x = Math.Max(x, x2);
y = Math.Max(y, y2);
// Find the largest change (pixel, not ratio)
double deltaX = x - width;
double deltaY = y - height;
// Return the ratio that will bring the largest change into the region
return (deltaX > deltaY) ? width / x : height / y;
}
Example of use:
private WriteableBitmap GenerateConstrainedBitmap(BitmapImage sourceImage, int pixelWidth, int pixelHeight, double rotation)
{
double scale = CalculateConstraintScale(rotation, pixelWidth, pixelHeight);
// Create a transform to render the image rotated and scaled
var transform = new TransformGroup();
var rt = new RotateTransform()
{
Angle = rotation,
CenterX = (pixelWidth / 2.0),
CenterY = (pixelHeight / 2.0)
};
transform.Children.Add(rt);
var st = new ScaleTransform()
{
ScaleX = scale,
ScaleY = scale,
CenterX = (pixelWidth / 2.0),
CenterY = (pixelHeight / 2.0)
};
transform.Children.Add(st);
// Resize to specified target size
var tempImage = new Image()
{
Stretch = Stretch.Fill,
Width = pixelWidth,
Height = pixelHeight,
Source = sourceImage,
};
tempImage.UpdateLayout();
// Render to a writeable bitmap
var writeableBitmap = new WriteableBitmap(pixelWidth, pixelHeight);
writeableBitmap.Render(tempImage, transform);
writeableBitmap.Invalidate();
return writeableBitmap;
}
I released a Test-bed of the code on my website so you can try it for real - click to try it
P.S. Yes this is my answer from another question, duplicated exactly, but the question does require the same answer as that one to be complete.

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