While the question title seems dumb, that's not exactly what I need. To fill whole area with color, one needs to select appropriate brush - that's trivial. But I want to fill upper half of it with different color, and bottom half of it with the different one. If it was the normal (not round) rectangle, I could draw two rectangles (with different brushes). But with RoundRect I don't have any ideas how to do it.
Here is what I need it for: I draw each node in my graph visualization with RoundRect, and those nodes should have several compartments (cells) that should be filled with different colors.
I hope you get the idea what I mean :)
If you have to use legacy GDI instead of GDI+, here I wrote you a function to draw such a (cell) as you needed I hope it is what you have expected !
The basic idea is to create upper and lower regions (which they were both full overlapping rounded rectangles, then each has one of its halves cut off)
I have prepared the above illustration to show how the cell could be produced. It's for the upper side only, but you should have got the idea of creating the lower one.
Here is a wrapping function to create the cell you need:
void DrawCell(HDC& hdc, const RECT& rcTarget,const HBRUSH& hbrUpper, const HBRUSH& hbrLower)
{
HRGN hRgnUpper = CreateRoundRectRgn(rcTarget.left, rcTarget.top, rcTarget.right, rcTarget.bottom, 42, 38);
HRGN hRgnLower = CreateRoundRectRgn(rcTarget.left, rcTarget.top, rcTarget.right, rcTarget.bottom, 42, 38);
HRGN hRgnCutFromUpper = CreateRectRgn(rcTarget.left, rcTarget.top + ((rcTarget.bottom - rcTarget.top) / 2), rcTarget.right, rcTarget.bottom);
HRGN hRgnCutFromLower = CreateRectRgn(rcTarget.left, rcTarget.top , rcTarget.right, rcTarget.bottom - ((rcTarget.bottom - rcTarget.top) / 2));
CombineRgn(hRgnUpper, hRgnUpper,hRgnCutFromUpper, RGN_DIFF);
CombineRgn(hRgnLower, hRgnLower,hRgnCutFromLower, RGN_DIFF);
FillRgn( hdc, hRgnUpper, hbrUpper);
FillRgn( hdc, hRgnLower, hbrLower);
DeleteObject(hRgnCutFromLower);
DeleteObject(hRgnCutFromUpper);
DeleteObject(hRgnLower);
DeleteObject(hRgnUpper);
}
call this function from within your WM_PAINT handler:
RECT rcTarget;
rcTarget.left = 20;
rcTarget.top = 20;
rcTarget.right = 275;
rcTarget.bottom = 188;
HBRUSH hRed = CreateSolidBrush( RGB(255, 0, 0) );
HBRUSH hGreen = CreateSolidBrush( RGB(0, 255, 0) );
DrawCell(hdc, rcTarget, hRed, hGreen);
Related
I am using the p5.js Web Editor
var sketch = function (p) {
with(p) {
p.setup = function() {
createCanvas(400, 400);
secCanvas = createGraphics(400, 400);
secCanvas.clear();
trans = 0;
drop_size = 10;
sun_size = 50;
radius = 10;
};
p.draw = function() {
background(3, 182, 252, 1);
image(secCanvas, 0, 0)
secCanvas.fill(255, 162, 0, 1)
secCanvas.ellipse(width/2, 0 + sun_size, sun_size)
fill(40, trans)
trans = random(255);
ellipse(random(mouseX + radius, mouseX - radius), random(mouseY + radius, mouseY - radius), drop_size)
drop_size = random(50)
};
}
};
let node = document.createElement('div');
window.document.getElementById('p5-container').appendChild(node);
new p5(sketch, node);
body {
background-color:#efefef;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.1.9/p5.js"></script>
<div id="p5-container"></div>
When I set a discrete value of alpha in secCanvas.fill(). The value appears to be gradually increase(and stops soon), while I gave no such instruction. Why is this happening? This only happens when I put background(3, 182, 252, 1); in the draw function but not when I put it in the setup function.
Each frame is drawn on top of all previous frames, so when you draw a semi-transparent background, you can still see the previous frames underneath it.
Think of it as adding a very thin coat of paint over top what you've already painted. Because the color you're adding is semi-transparent, you can still see what's underneath it. Then during the next frame, you add another layer of paint, and the previous frames get just a little more faint.
They stop becoming more faint because of the way the computer calculates the new color, based on the previous frames and the new semi-transparent background color. Long story short, the color you're drawing is almost 100% transparent, so it's not strong enough to completely hide previous frames.
Overview
In my app (which is a game), I make use of the batching of items to reduce the number of draw calls. So, I'll, create for example, a Java object called platforms which is for all the platforms in the game. All the enemies are batched together as are all collectible items etc....
This works really well. At present I am able to size and position the individual items in a batch independently of each other however, I've come to the point where I really need to change the opacity of individual items also. Currently, I can change only the opacity of the entire batch.
Batching
I am uploading the vertices for all items within the batch that are to be displayed (I can turn individual items off if I don't want them to be drawn), and then once they are all done, I simply draw them in one call.
The following is an idea of what I'm doing - I realise this may not compile, it is just to give an idea for the purpose of the question.
public void draw(){
//Upload vertices
for (count = 0;count<numOfSpritesInBatch;count+=1){
vertices[x] = xLeft;
vertices[(x+1)] = yPTop;
vertices[(x+2)] = 0;
vertices[(x+3)] = textureLeft;
vertices[(x+4)] = 0;
vertices[(x+5)] = xPRight;
vertices[(x+6)] = yTop;
vertices[(x+7)] = 0;
vertices[(x+8)] = textureRight;
vertices[x+9] = 0;
vertices[x+10] = xLeft;
vertices[x+11] = yBottom;
vertices[x+12] = 0;
vertices[x+13] = textureLeft;
vertices[x+14] = 1;
vertices[x+15] = xRight;
vertices[x+16] = yTop;
vertices[x+17] = 0;
vertices[x+18] = textureRight;
vertices[x+19] = 0;
vertices[x+20] = xLeft;
vertices[x+21] = yBottom;
vertices[x+22] = 0;
vertices[x+23] = textureLeft;
vertices[x+24] = 1;
vertices[x+25] = xRight;
vertices[x+26] = yBottom;
vertices[x+27] = 0;
vertices[x+28] = textureRight;
vertices[x+29] = 1;
x+=30;
}
vertexBuf.rewind();
vertexBuf.put(vertices).position(0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texID);
GLES20.glUseProgram(iProgId);
Matrix.multiplyMM(mvpMatrix2, 0, mvpMatrix, 0, mRotationMatrix, 0);
mMVPMatrixHandle = GLES20.glGetUniformLocation(iProgId, "uMVPMatrix");
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix2, 0);
vertexBuf.position(0);
GLES20.glVertexAttribPointer(iPosition, 3, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iPosition);
vertexBuf.position(3);
GLES20.glVertexAttribPointer(iTexCoords, 2, GLES20.GL_FLOAT, false, 5 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iTexCoords);
//Enable Alpha blending and set blending function
GLES20.glEnable(GLES20.GL_BLEND);
GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA);
//Draw it
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 6 * numOfSpritesInBatch);
//Disable Alpha blending
GLES20.glDisable(GLES20.GL_BLEND);
}
Shaders
String strVShader =
"uniform mat4 uMVPMatrix;" +
"attribute vec4 a_position;\n"+
"attribute vec2 a_texCoords;" +
"varying vec2 v_texCoords;" +
"void main()\n" +
"{\n" +
"gl_Position = uMVPMatrix * a_position;\n"+
"v_texCoords = a_texCoords;" +
"}";
String strFShader =
"precision mediump float;" +
"uniform float opValue;"+
"varying vec2 v_texCoords;" +
"uniform sampler2D u_baseMap;" +
"void main()" +
"{" +
"gl_FragColor = texture2D(u_baseMap, v_texCoords);" +
"gl_FragColor *= opValue;"+
"}";
Currently, I have a method in my Sprite class that allows me to change the opacty. For example, something like this:
spriteBatch.setOpacity(0.5f); //Half opacity
This works, but changes the whole batch - not what I'm after.
Application
I need this because I want to draw small indicators when the player destroys an enemy - which show the score obtained from that action. (The type of thing that happens in many games) - I want these little 'score indicators' to fade out once they appear. All the indicators would of course be created as a batch so they can all be drawn with one draw call.
The only other alternatives are:
Create 10 textures at varying levels of opacity and just switch between them to create the fading effect. Not really an option as way too wasteful.
Create each of these objects separately and draw each with their own draw call. Would work, but with a max of 10 of these objects on-screen, I could potentially be drawing using 10 draw calls just for these items - while the game as a whole currently only uses about 20 draw calls to draw a hundreds of items.
I need to look at future uses of this too in particle systems etc.... so I would really like to try to figure out how to do this (be able to adjust each item's opacity separately). If I need to do this in the shader, I would be grateful if you could show how this works. Alternatively, is it possible to do this outside of the shader?
Surely this can be done in some way or another? All suggestions welcome....
The most direct way of achieving this is to use a vertex attribute for the opacity value, instead of a uniform. This will allow you to set the opacity per vertex, without increasing the number of draw calls.
To implement this, you can follow the pattern you already use for the texture coordinates. They are passed into the vertex shader as an attribute, and then handed off to the fragment shader as a varying variable.
So in the vertex shader, you add:
...
attribute float a_opValue;
varying float v_opValue;
...
v_opValue = a_opValue;
...
In the fragment shader, you remove the uniform declaration for opValue, and replace it with:
varying float v_opValue;
...
gl_FragColor *= v_opValue;
...
In the Java code, you extend the vertex data with an additional value for the opacity, to use 6 values per vertex (3 position, 2 texture coordinates, 1 opacity), and update the state setup accordingly:
vertexBuf.position(0);
GLES20.glVertexAttribPointer(iPosition, 3, GLES20.GL_FLOAT, false, 6 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iPosition);
vertexBuf.position(3);
GLES20.glVertexAttribPointer(iTexCoords, 2, GLES20.GL_FLOAT, false, 6 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iTexCoords);
vertexBuf.position(5);
GLES20.glVertexAttribPointer(iOpValue, 1, GLES20.GL_FLOAT, false, 6 * 4, vertexBuf);
GLES20.glEnableVertexAttribArray(iOpValue);
I want to create a colour scroller effect. I have a function that I give it RGB values (eg. setColor(189,234,45)) and I want to change the colour rapidly but I don't want to get many repeats to create an effect of scrolling through the colours.
I have tried tried the following but it doesn't quite generate the effect that I am looking for.
for (int i = 0; i < 256; i++) {
for (int j = 0; j < 256; j++) {
for (int k = 0; k < 256; k++) {
setColor(i, j, k);
}
}
}
I wanted to know if anyone knows how the colour scroller's colours are arranged next to each other. The arrangement I am looking for looks like the scroll on the right.
The colors you are working with are represented as R,G,B (red green blue) values. However, another
way to think about color is hue, saturation, value. In the scroll image you are trying to emulate,
it is the hue that is changing - the saturation and value (brightness) are unaffected.
Here is a function that happens to make a hue-cycle gradient like the one in the image you linked to:
int n = 256; // number of steps
float TWO_PI = 3.14159*2;
for (int i = 0; i < n; ++i) {
int red = 128 + sin(i*TWO_PI/n + 0) + 127;
int grn = 128 + sin(i*TWO_PI/n + TWO_PI/3) + 127;
int blu = 128 + sin(i*TWO_PI/n + 2*TWO_PI/3) + 127;
setColor(red, grn, blu);
}
To understand how that function works, I recommend that you read my color tutorial that GreenAsJade linked to.
However, that kind of gradient function isn't quite what you need, because you want to start from a particular color you are passing in, and then go to the next color in the sequence. It's much easier to do this kind of thing if you represent your colors as HSV triplets (or HSB triplets), instead of RGB triplets. Then you can manipulate just the hue component, and get those kind of rainbow effects. In helps to have a set of function that can convert from RGB to HSV and back again.
This site contains a bunch of color conversion source code, including the ones you need for those conversions. Using the two conversion functions supplied on that page, your code might look like:
void cycleMyColor(int *r, int *g, int *b) {
float h,s,v, fr,fg,fb;
RGBtoHSV(*r/255.0,*g/255.0,*b/255.0,&h,&s,&v);
h += 1/256.0; // increment the hue here
h -= (int) h; // and cycle around if necessary
HSVtoRGB(&fr,&fg,&fb,h,s,v);
*r = fr*255; *g = fg*255; *b = fb*255;
setColor(*r,*g,*b);
}
This code is a little more complicated than it needs to be because the color conversions on that site use floating point color components that go from 0-1, instead of integers that go from 0-255, as you were using, so I'm spending a few lines converting between those two representations. You may find it simpler to just keep your color in HSB space, and then convert to RGB when you want to display it.
As you mentioned in your edit, you don't like the sequence of colours, because you start from black an end at white, instead of starting at one end of the rainbow and going to the other.
So you are going to need to work out a sequence of RGB that goes from blue through green and yellow to red. That means you need to start with (0,0,255) and end at (255, 0, 0), and don't pass through (255,255,255) or (0,0,0) - in a nutshell, that's how its done.
There are many ways you could do this and get a pleasing effect - beyond the scope of an answer here. This article explores it in depth:
http://krazydad.com/tutorials/makecolors.php
Is there any way to fill an ellipse or a rect by point to point like in an airbrush tool in mspaint?
I could not find a way to create an empty rect or an ellipse and then fill them up pixel by pixel or setting random pixels on screen in a circle way....
Can i tell setPixel to fill inside a dcellipse or anything like that?
10x
You need to create a region with CRgn, then select that as the clipping region in your CDC with SelectClipRgn. Then you can use CDC::SetPixel to set random pixels anywhere within the bounding rectangle of your shape, and only the ones within the clipping region will be painted.
Be aware that this will be slow, and will need to be redone every time the window paints (such as when another window is dragged over it).
In your "make random pixels" loop, just exclude the pixel if it's outside your desired circle.
num_pixels = 20; // how many pixels
circle_radius = 32; // 32-pixel radius, or whatever you'd like
circle_radius2 = circle_radius * circle_radius;
while (num_pixels-- > 0)
{
// get a random number between (-circle_radius / 2, circle_radius / 2)
pixel_x = rand(circle_radius) - circle_radius / 2;
pixel_y = rand(circle_radius) - circle_radius / 2;
// compute squared distance between generated pixel and radius,
// exclude if out of range
if ( (center_x - pixel_x) * (center_x - pixel_x) +
(center_y - pixel_y) * (center_y - pixel_y) > circle_radius2 )
continue; // generate another pixel
// do stuff with pixel
}
Given two colors and n steps, how can one calculate n colors including the two given colors that create a fade effect?
If possible pseudo-code is preferred but this will probably be implemented in Java.
Thanks!
Divide each colour into its RGB components and then calculate the individual steps required.
oldRed = 120;
newRed = 200;
steps = 10;
redStepAmount = (newRed - oldRed) / steps;
currentRed = oldRed;
for (i = 0; i < steps; i++) {
currentRed += redStepAmount;
}
Obviously extend that for green and blue.
There are two good related questions you should also review:
Generating gradients programatically?
Conditional formatting — percentage to color conversion
Please note that you're often better off doing this in the HSV color space rather than RGB - it generates more pleasing colors to the human eye (lower chance of clashing or negative optical properties).
Good luck!
-Adam
If you want a blend that looks anything like most color picker GUI widgets, you really want to translate to HSL or HSV. From there, you're probably fine with linear interpolation in each dimension.
Trying to do any interpolations directly in RGB colorspace is a bad idea. It's way too nonlinear (and no, gamma correction won't help in this case).
For those looking for something they can copy and paste. Made a quick function for RGB colors. Returns a single color that is the amount of ratio closer to rgbColor2.
function fadeToColor(rgbColor1, rgbColor2, ratio) {
var color1 = rgbColor1.substring(4, rgbColor1.length - 1).split(','),
color2 = rgbColor2.substring(4, rgbColor2.length - 1).split(','),
difference,
newColor = [];
for (var i = 0; i < color1.length; i++) {
difference = color2[i] - color1[i];
newColor.push(Math.floor(parseInt(color1[i], 10) + difference * ratio));
}
return 'rgb(' + newColor + ')';
}
The quesiton is what transformation do you want to occur? If you transpose into the HSV colourspace and given
FF0000 and 00FF00
It will transition from red through yellow to green.
However, if you define "black" or some other shade as being the mid-point of the blend, you have to shade to that colour first ff0000->000000->00ff00 or via white : ff0000 -> ffffff -> 00ff00.
Transforming via HSV however can be fun because you have to use a bit of trig to map the circular map into the vector components.
The easiest thing to do is linear interpolation between the color components (see nickf's response). Just be aware that the eye is highly nonlinear, so it won't necessarily look you're making even steps. Some color spaces attempt to address this (CIE maybe?), so you might want to transform into another color space first, interpolate, then transform back to RGB or whatever you're using.
How about this answer
- (UIColor *)colorFromColor:(UIColor *)fromColor toColor:(UIColor *)toColor percent:(float)percent
{
float dec = percent / 100.f;
CGFloat fRed, fBlue, fGreen, fAlpha;
CGFloat tRed, tBlue, tGreen, tAlpha;
CGFloat red, green, blue, alpha;
if(CGColorGetNumberOfComponents(fromColor.CGColor) == 2) {
[fromColor getWhite:&fRed alpha:&fAlpha];
fGreen = fRed;
fBlue = fRed;
}
else {
[fromColor getRed:&fRed green:&fGreen blue:&fBlue alpha:&fAlpha];
}
if(CGColorGetNumberOfComponents(toColor.CGColor) == 2) {
[toColor getWhite:&tRed alpha:&tAlpha];
tGreen = tRed;
tBlue = tRed;
}
else {
[toColor getRed:&tRed green:&tGreen blue:&tBlue alpha:&tAlpha];
}
red = (dec * (tRed - fRed)) + fRed;
green = (dec * (tGreen - fGreen)) + fGreen;
blue = (dec * (tBlue - fBlue)) + fBlue;
alpha = (dec * (tAlpha - fAlpha)) + fAlpha;
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}