Angular Download Canvas Image

I have an image i am getting from a url. I want to display this image in a canvas but when it gives me error image not found but my image is present in a folder and I have given its path correclty. Tell me why it is saying image not found?

Trying to add a background image to canvas using drawImage and it's not showing up. I know the path to the image is correct because I can do and that works. Everything else works fine in JavaScript but doesn't translate well to Angular.

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An element to draw into the context. The specification permits any canvas image source, specifically, an HTMLImageElement, an SVGImageElement, an HTMLVideoElement, an HTMLCanvasElement, an ImageBitmap, an OffscreenCanvas, or a VideoFrame.

The width of the sub-rectangle of the source image to draw into the destination context. If not specified, the entire rectangle from the coordinates specified by sx and sy to the bottom-right corner of the image is used. Use the 3- or 5-argument syntax to omit this argument. A negative value will flip the image.

The width to draw the image in the destination canvas. This allows scaling of the drawn image. If not specified, the image is not scaled in width when drawn. Note that this argument is not included in the 3-argument syntax.

The height to draw the image in the destination canvas. This allows scaling of the drawn image. If not specified, the image is not scaled in height when drawn. Note that this argument is not included in the 3-argument syntax.

\n An element to draw into the context. The specification permits any canvas image\n source, specifically,\n an HTMLImageElement,\n an SVGImageElement,\n an HTMLVideoElement,\n an HTMLCanvasElement,\n an ImageBitmap,\n an OffscreenCanvas,\n or a VideoFrame.\n

\n The width of the sub-rectangle of the source image to draw into the\n destination context. If not specified, the entire rectangle from the coordinates\n specified by sx and sy to the bottom-right corner of the\n image is used. Use the 3- or 5-argument syntax to omit this argument.\n A negative value will flip the image.\n

\n The width to draw the image in the destination canvas. This allows\n scaling of the drawn image. If not specified, the image is not scaled in width when\n drawn. Note that this argument is not included in the 3-argument syntax.\n

\n The height to draw the image in the destination canvas. This allows\n scaling of the drawn image. If not specified, the image is not scaled in height when\n drawn. Note that this argument is not included in the 3-argument syntax.\n

I'm just messing around with HTML 5 canvas in angular. I successfully managed to draw. a red square on the canvas. Now I'm trying to add an png image to it but the image is not showing. Can anybody spot my mistake ? the code is below.

We'll go over the parameters mentioned above one by one, in a way that'll make complete sense to you. If at any point in the article you find yourself going "I just wanted to draw an image on my canvas dear Nash. Why put my mind through a ringer?", it'll be an understandable frustration.

By the end of this article you'll be able to visualise how drawImage will draw any given image on canvas just by looking at the values of the 9 parameters. Sounds like a superpower you might wanna have? Okay then, let's dive right in!

We need myContext to interact with the canvas element. It's like, if canvas is a blank sheet of paper, the canvas's context is the pen. Intuitively, you'll tell your pen to draw something on a blank sheet of paper, and not just yell at the paper to draw something on itself right?

There is a number of things you can do with context. You can draw a rectangle, or an ellipse or a line, or, an... image. Also, notice that the context myContext is implicitly linked to myCanvas. You can have multiple canvass and call getContext() on each of them to get a new context/pen for each. In our case we are dealing with just one canvas (myCanvas) and just one context (myContext).

That is something you didn't expect, did you? Canvas needs a preloaded image in order to draw/display it in itself. No need to show any contempt towards canvas by the way. It has its reason, it's just like the rest of us. We'll eventually see what those reasons are and maybe then you'll be able to sympathise.

drawImage asks for 9 parameters, first of which is image. We looked and understood that canvas requires a preloaded image to draw and not just a URI to the image. Why does it need that? It will become clear as you read.

Every single, even the most basic of graphics editing programs come with the feature of cropping. It's fairly simple, open an image > select the area you want visible > hit crop. And just like that the naked beer belly of that obnoxious smelling old man is out. Poof!

The first task drawImage performs--behind the scenes--is it selects a portion of the image based on the four s parameters (sx, sy, sWidth, sHeight). You can say that s in all the s.. parameters stands for "select".

Here's how it goes. sx and sy mark the point on the image from where the selection is to begin, or in other words the coordinates of the top left corner of the selection rectangle. sWidth and sHeight then, are the width and height of the selection rectangle respectively. You can scroll right up to the last image to get a clearer picture of what I am trying to explain.

Remember that you don't always have to select a small portion of the image, you can select the entire image if you want to. In that case sx and sy will have values 0 and 0 respectively and sWidth, sHeight will be the same as the image's width and height.

There's a very important but subtle detail to notice here. dWidth and dHeight are in no way tied to sWidth and sHeight. They are independent values. Why do you need to know that? Well, because if you don't choose values of the width and height of 'draw' carefully you will end up with a stretched or squashed image, like this.

That is all! In this case you're telling drawImage only the location on canvas where to start the drawing. The rest, sx, sy, sWidth, sHeight, dWidth and dHeight are taken care of automagically. The method selects the entire image (sx = 0, sy = 0, sWidth = image's width, sHeight = images' height) and starts drawing on canvas at (dx, dy) with dWidth and dHeight same as sWidth(image's width), sHeight(image's height) .

Well, a 50% yes. Imagine how resource intensive storing and loading a huge set of images describing every frame of animation in our program (or game) would be. Instead, there's a single image and all the positions are laid out in a grid. Like the one shown below.

Next, in the // Selection block we defined the area of the image we want to select, in the // Drawing section we defined the width and height and the position from where to start drawing on the canvas... aaand just like that we managed to draw just one cell of the entire imaginary grid.

So now we have Mario in the canvas, small and little. We need to animate it, or in other words show different frames at the same location in succession and make the illusion of movement happen. Was I too specific? Heck yeah!

Note: In some cases, img.src= is currently synchronous. However, you should always use img.onload and img.onerror, as we intend to make img.src= always asynchronous as it is in browsers. See -canvas/issues/1007.

Setting img.dataMode = Image.MODE_MIME or Image.MODE_MIME|Image.MODE_IMAGE enables MIME data tracking of images. When MIME data is tracked, PDF canvases can embed JPEGs directly into the output, rather than re-encoding into PNG. This can drastically reduce filesize and speed up rendering.

For image/jpeg, an object specifying the quality (0 to 1), if progressive compression should be used and/or if chroma subsampling should be used: {quality: 0.75, progressive: false, chromaSubsampling: true}. All properties are optional.

For image/png, an object specifying the ZLIB compression level (between 0 and 9), the compression filter(s), the palette (indexed PNGs only), the the background palette index (indexed PNGs only) and/or the resolution (ppi): {compressionLevel: 6, filters: canvas.PNG_ALL_FILTERS, palette: undefined, backgroundIndex: 0, resolution: undefined}. All properties are optional.

PDF glyph will embed text instead of paths into the PDF. This is faster to encode, faster to open with PDF viewers, yields a smaller file size and makes the text selectable. The subset of the font needed to render the glyphs will be embedded in the PDF. This is usually the mode you want to use with PDF canvases.

If librsvg is available when node-canvas is installed, node-canvas can render SVG images to your canvas context. This currently works by rasterizing the SVG image (i.e. drawing an SVG image to an SVG canvas will not preserve the SVG data).

By default, canvases are created in the RGBA32 format, which corresponds to the native HTML Canvas behavior. Each pixel is 32 bits. The JavaScript APIs that involve pixel data (getImageData, putImageData) store the colors in the order {red, green, blue, alpha} without alpha pre-multiplication. (The C++ API stores the colors in the order {alpha, red, green, blue} in native-endian ordering, with alpha pre-multiplication.)

All the numbers in the drawing change dynamically with changing data from a web-service, but are located within the canvas that the png image is in too, so there is not html/css positioning nightmare.

Canvas gives us a lot of flexibility to create great, code generated graphics, and sometimes we need to download them as images. Fortunately, this is quite easy with HTML canvas. Here is an example, where clicking the button downloads the canvas as an image:

In the example above, we've created a canvas image and a button you can click to download it. This button uses toDataURL() to convert our canvas to an image URL data string. When we click on it we get our original canvas, and then create an anchor to download it immediately:

Saving canvas elements as images is straightforward and only relies on toDataURL. If you want to learn about saving canvas images in a real world setting on the backend, you can read my tutorial on that here. ff782bc1db