Ok, so I'm doing an html5 canvas game, and I need to draw resized images all the time (it's all pixel-art). Unfortunately, doing the resizing on drawImage makes current browsers quite sluggish, so I'm trying to do the resizing on load, and then just draw the pre-resized image.
I've tried to draw the resized images to a hidden context and then do a ctx.getImageData, but then I'm stuck with a byte array and there's no way to convert to an image. I can do a putImageData to push it to the final context, but that's slow and I apparently lose the alpha channel.
Another option could be to pre-scale things in the server, but I'd like to avoid that if at all possible.
Any ideas?
There is a method on the canvas object (not the context) called toDataURL(string mimeType), this will convert the canvas contents to a base64-encoded binary string of an image. You can use this as the src attribute of any image element.
ctx.drawImage(originalImage, 0, 0, originalImage.width, originalImage.height, 0, 0, 200, 200);
var scaledImage = new Image();
scaledImage.onload = ...;
scaledImage.src = canvas.toDataURL("image/png");
Now you can draw your scaled image normaly.
Related
I get an image from the backend which I want to put in a puzzle shuffle game, however right now it is cropping from left to almost middle of the image , I would like to crop the center of the image, I was trying to use another Sprite which I cropped to the middle then use it in the ImageSlicer however I am getting same results.
Here are the images :
Main Image , Cropped Image as temp , Sliced Image as imagesSlices
am I doing the right thing and maybe I'm messing something in the code or this isn't how I should crop and slice ?
Sprite temp = Sprite.Create(currentImage, new Rect(currentImage.width * 0.25f, 0, currentImage.width * 0.75f, currentImage.height),new Vector2(0.5f, 0.5f), 100.0f);
Texture2D[,] imageSlices = ImageSlicer.GetSlices(temp.texture, blocksPerLine);
So the texture was staying the same and I was trying to get a new sprite not a new texture but I need a new cropped texture to work with which is why the sliced images were taken from old texture.
I am desperately searching for a good cropping tool. There are a bunch out there, for example:
Croppic
Cropit
Jcrop
The most important thing that I am trying to find is a cropping tool, that crops images without making the cropped image low in resolution. You can hack this by using the canvas tag by resizing the image. This way the image itself stays native, only the representation is smaller.
DarkroomJS was also something near the solution, but, unfortunately, the downloaded demo did not work. I'll try to figure out whats wrong. Does someone know some great alternatives, or how to get the cropped images in...let's say "native" resolution?
Thanks in advance!
You are relying on the cropping tool to provide an interface for the users. the problem is that the image returned is sized to the interface and not the original image. Rather than me sifting through the various API's to see if they provide some way of controlling this behaviour (I assume at least some of them would) and because it is such a simple procedure I will show how to crop the image manually.
To use JCrop as an example
Jcrop provides various events for cropstart, cropmove, cropend... You can add a listener to listen to these events and keep a copy of the current cropping interface state
var currentCrop;
jQuery('#target').on('cropstart cropmove cropend',function(e,s,crop){
currentCrop = crop;
}
I don't know where you have set the interface size and I am assuming the events return the crop details at the interface scale
var interfaceSize = { //you will have to work this out
w : ?,
h : ?.
}
Your original image
var myImage = new Image(); // Assume you know how to load
So when the crop button is clicked you can create the new image by scaling the crop details back to the original image size, creating a canvas at the cropped size, drawing the image so that the cropped area is corectly positioned and returning the canvas as is or as a new image.
// image = image to crop
// crop = the current cropping region
// interfaceSize = the size of the full image in the interface
// returns a new cropped image at full res
function myCrop(image,crop,interfaceSize){
var scaleX = image.width / interfaceSize.w; // get x scale
var scaleY = image.height / interfaceSize.h; // get y scale
// get full res crop region. rounding to pixels
var x = Math.round(crop.x * scaleX);
var y = Math.round(crop.y * scaleY);
var w = Math.round(crop.w * scaleX);
var h = Math.round(crop.h * scaleY);
// Assume crop will never pad
// create an drawable image
var croppedImage = document.createElement("canvas");
croppedImage.width = w;
croppedImage.height = h;
var ctx = croppedImage.getContext("2d");
// draw the image offset so the it is correctly cropped
ctx.drawImage(image,-x,-y);
return croppedImage
}
You then only need to call this function when the crop button is clicked
var croppedImage;
myButtonElement.onclick = function(){
if(currentCrop !== undefined){ // ensure that there is a selected crop
croppedImage = myCrop(myImage,currentCrop,interfaceSize);
}
}
You can convert the image to a dataURL for download, and upload via
imageData = croppedImage.toDataURL(mimeType,quality) // quality is optional and only for "image/jpeg" images
My question is related to this previous question. What I want to achieve is to stack images (they have transparency), write a string on top, and save the photomontage / photocollage with full resolution.
#Override
protected void beforeMain(Form f) {
Image photoBase = fetchResourceFile().getImage("Voiture_4_3.jpg");
Image watermark = fetchResourceFile().getImage("Watermark.png");
f.setLayout(new LayeredLayout());
final Label drawing = new Label();
f.addComponent(drawing);
// Image mutable dans laquelle on va dessiner (fond blanc)
Image mutableImage = Image.createImage(photoBase.getWidth(), photoBase.getHeight());
drawing.getUnselectedStyle().setBgImage(mutableImage);
drawing.getUnselectedStyle().setBackgroundType(Style.BACKGROUND_IMAGE_SCALED_FIT);
// Paint all the stuff
paints(mutableImage.getGraphics(), photoBase, watermark, photoBase.getWidth(), photoBase.getHeight());
// Save the collage
Image screenshot = Image.createImage(photoBase.getWidth(), photoBase.getHeight());
f.revalidate();
f.setVisible(true);
drawing.paintComponent(screenshot.getGraphics(), true);
String imageFile = FileSystemStorage.getInstance().getAppHomePath() + "screenshot.png";
try(OutputStream os = FileSystemStorage.getInstance().openOutputStream(imageFile)) {
ImageIO.getImageIO().save(screenshot, os, ImageIO.FORMAT_PNG, 1);
} catch(IOException err) {
err.printStackTrace();
}
}
public void paints(Graphics g, Image background, Image watermark, int width, int height) {
g.drawImage(background, 0, 0);
g.drawImage(watermark, 0, 0);
g.setColor(0xFF0000);
// Upper left corner
g.fillRect(0, 0, 10, 10);
// Lower right corner
g.setColor(0x00FF00);
g.fillRect(width - 10, height - 10, 10, 10);
g.setColor(0xFF0000);
Font f = Font.createTrueTypeFont("Geometos", "Geometos.ttf").derive(220, Font.STYLE_BOLD);
g.setFont(f);
// Draw a string right below the M from Mercedes on the car windscreen (measured in Gimp)
g.drawString("HelloWorld",
(int) (848 ),
(int) (610)
);
}
This is the saved screenshot I get if I use the Iphone6 skin (the payload image is smaller than the original one and is centered). If I use the Xoom skin this is what I get (the payload image is still smaller than the original image but it has moved to the left).
So to sum it all up : why is the saved screenshot with Xoom skin different from the one I get with Iphone skin ? Is there anyway to directly save the graphics on which I paint in the paints method so that the saved image would have the original dimensions ?
Thanks a lot to anyone that could help me :-)!
Cheers,
You can save an image in Codename one using the ImageIO class. Notice that you can draw a container hierarchy into a mutable image using the paintComponent(Graphics) method.
You can do both approaches with draw image on mutable or via layouts. Personally I always prefer layouts as I like the abstraction but I wouldn't say the mutable image approach is right/wrong.
Notice that if you change/repaint a lot then mutable images are slower (this will not be noticeable for regular code or on the simulator) as they are forced to use the software renderer and can't use the GPU fully.
In the previous question it seems you placed the image with a "FIT" style which naturally drew it smaller than the containing container and then drew the image on top of it manually... This is problematic.
One solution is to draw everything manually but then you will need to do the "fit" aspect of drawing yourself. If you use layouts you should position everything based on the layouts including your drawing/text.
I load an image (NSImage) from the disk, and draw it to an NSImageView on MAC, No problem image looks fine and clear.
After drawing it to the NSImageView, I call the function below with the same image, then draw the returned value to the same NSImageView. The resulting image is extremly blurry, even if all I do is lockFocus and UnlockFocus without doing anything else.
-(NSImage*)addTarget:(NSImage*)image
{
[image lockFocus]; // this image is sharp and clear
[image unlockFocus];
return image; // this image is extremely blurry
}
Anybody knows why or how to fix that?
thanks
rough
So as doing some research I realized that this is related to Retina displays. I guess locking focus will always draw at bestRepresentation which if there is a retina display attached anywhere to the computer, it will render based on that scale factor. So in order to get this to maintain proper dimensions and DPI I created a method that iterates through all screens and returns the largest backingScaleFactor
func maximumScaleFactor(screen: NSScreen) -> CGFloat {
var max: CGFloat = 0
for s in NSScreen.screens()! {
if s.backingScaleFactor > max { max = s.backingScaleFactor }
}
return max / screen.backingScaleFactor
}
Then for the 'NSImage' I did the following
-(NSImage*)addTarget:(NSImage*)image
let scale = self.maximumScaleFactor(currentScreen)
let originalSize = image.size
//cut the image size in half
var size = image.size
size.x /= scale
size.y /= scale
image.lockFocus()
//do whatever drawing you need here
image.unlockFocus()
//set the image back to its original size
image.size = originalSize
return image
}
So far this has worked well for me and the image quality subjectively appears the same to me.
To fix your problem is difficult because you don't say what you want to achieve. Why did you write that method, why do you call it, what do you expect this method does? You said: all I do is lockFocus and UnlockFocus without doing anything else. Indeed it looks like calling lockFocus unlockFocus (and nothing between) does nothing. But that is wrong. [image lockFocus] alone changes image dramatically. An NSImage object contains zero, one (in most cases) or more (icon or some TIFFs) object of class NSImageRep. A call of lockFocus on this image selects an NSImageRep, that is best suited for depicting on the screen. Then it computes how many pixels (but now for a screen) it needs to render the image with the given size but with a resolution of only 72 dpi (or 144 dpi for retina screens). And then removes the NSImageRep from the list of representations and creates instead a new NSImageRep. In former OS-versions (before 10.6) an NSCachedImageRep was created. But now an NSCGImageSnapshotRep is created which under the hood is a CGImage. Make a
NSLog(#" image is:\n%#", image );
before lockFocus and one after the call of unlockFocus and the you will see what happens: for a high resolution image the number of pixels will go down, which is a nothing else than a reduction in quality. And that makes your image blurry.
I load a PNG image in a QPixmap/QImage and I want to crop it. Is there a function that does that in Qt, or how should I do it otherwise?
You can use QPixmap::copy:
QRect rect(10, 20, 30, 40);
QPixmap original('image.png');
QPixmap cropped = original.copy(rect);
There is also QImage::copy:
QRect rect(10, 20, 30, 40);
QImage original('image.png');
QImage cropped = original.copy(rect);
Use QImage instead of QPixmap:
QImage image("initial_image.jpg");
QImage copy ;
copy = image.copy( 0, 0, 128, 128);
copy.save("cropped_image.jpg");
This code will save a file cropped to upper left corner 128x128px.
Since you use QPixmap, you can use its copy method and supply it with a QRect to perform the actual crop.
Just use of the QPixmap's copy() functions.
This text is result of reading the first comment on your quiestion:
Sometimes it is better to wrap around an image. That is to have an image that is part of another image or in other words points to a part of another image. This is way the wrapped image does not require additional memory, except for its header. You can display or save the wrapped image without worries. The downside is that the original image must remain valid until you use the wrapped image, also if you are drawing in the wrapped image it will affect the source.