How to: Create a Bitmap at Run Time
This resulted in the following code:. I also noticed that the encoding of the. I thought that this mean that I have to reverse the order of the bytes. For example, in four bytes is:and I think in little endian this would be: Your pixel offset bytes Your horizontal and vertical resolutions have the wrong byte order, but I very much doubt that that matters.
If I were doing this I'd define structs for the header data indeed, if you're on Windows, Microsoft have already done this and use a macro or something for putting bytes into the right order portably. Whether you "have to reverse the order of the bytes" depends on the endianity of the processor you're using. Writing separate bytes separately, as you're doing, is an effective way to avoid having to worry about this. Open your file with a hex editor to see what is actually there.
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. A bitmap is an array of bits.
How is it implemented in C? I assume you're asking how to implement a bit map or bit array in C. Learn more. What is a bitmap in C? Ask Question. Asked 10 years, 8 months ago. Active 1 year, 10 months ago.Bitmap Images
Viewed 38k times. George Stocker Active Oldest Votes. Dan Grahn 7, 2 2 gold badges 28 28 silver badges 59 59 bronze badges. Dale Hagglund Dale Hagglund Sign up or log in Sign up using Google.
Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Cryptocurrency-Based Life Forms. Q2 Community Roadmap. Featured on Meta. Community and Moderator guidelines for escalating issues via new response…. Feedback on Q2 Community Roadmap. Triage needs to be fixed urgently, and users need to be notified upon….This article explains how to load and save image files using BitmapDecoder and BitmapEncoder and how to use the SoftwareBitmap object to represent bitmap images.
SoftwareBitmap allows you to easily convert between different pixel formats and alpha modes, and allows low-level access to pixel data. Also, SoftwareBitmap is a common interface used by multiple features of Windows, including:.
CapturedFrame allows you to get frames captured by the camera as a SoftwareBitmap. FaceDetector allows you to detect faces in a SoftwareBitmap. To create a SoftwareBitmap from a file, get an instance of StorageFile containing the image data.
This example uses a FileOpenPicker to allow the user to select an image file. Call the OpenAsync method of the StorageFile object to get a random access stream containing the image data. Call the static method BitmapDecoder. CreateAsync to get an instance of the BitmapDecoder class for the specified stream. To save a SoftwareBitmap to a file, get an instance of StorageFile to which the image will be saved. This example uses a FileSavePicker to allow the user to select an output file.
Call the OpenAsync method of the StorageFile object to get a random access stream to which the image will be written. Call the static method BitmapEncoder. CreateAsync to get an instance of the BitmapEncoder class for the specified stream. BitmapEncoder class exposes a property containing the ID for each codec supported by the encoder, such as JpegEncoderId.
Use the SetSoftwareBitmap method to set the image that will be encoded. You can set values of the BitmapTransform property to apply basic transforms to the image while it is being encoded.
The IsThumbnailGenerated property determines whether a thumbnail is generated by the encoder. Note that not all file formats support thumbnails, so if you use this feature, you should catch the unsupported operation error that will be thrown if thumbnails are not supported.
Call FlushAsync to cause the encoder to write the image data to the specified file. You can specify additional encoding options when you create the BitmapEncoder by creating a new BitmapPropertySet object and populating it with one or more BitmapTypedValue objects representing the encoder settings.
For a list of supported encoder options, see BitmapEncoder options reference. Currently, the Image control only supports images that use BGRA8 encoding and pre-multiplied or no alpha channel. Before attempting to display an image, test to make sure it has the correct format, and if not, use the SoftwareBitmap static Convert method to convert the image to the supported format.
Create a new SoftwareBitmapSource object. The second argument allows you to request a pixel format for the newly created WriteableBitmap. You can use the PixelWidth and PixelHeight properties of the WriteableBitmap to specify the dimensions of the new image.
So far this topic has addressed working with image files. You can also create a new SoftwareBitmap programatically in code and use the same technique to access and modify the SoftwareBitmap 's pixel data. SoftwareBitmap uses COM interop to expose the raw buffer containing the pixel data.
To use COM interop, you must include a reference to the System. InteropServices namespace in your project. Create a new SoftwareBitmap with pixel format and size you want. Or, use an existing SoftwareBitmap for which you want to edit the pixel data.
Code Review Stack Exchange is a question and answer site for peer programmer code reviews. It only takes a minute to sign up. Here's my function that creates a bitmap file from an array of pixels. It can write a bitmap both with transparency and without transparency. Please review my code and give constructive criticism on how to increase the overall quality of it.
I'm not sure that the inline specifier serves any purpose here. Compilers generally ignore inline suggestions anyway, but in this case I can't see this entire huge function being something you'd want to inline. If you added it to get a header-only library function, that makes sense, but this doesn't really seem like a candidate for a header-only library. I don't really see the benefit of taking bit integers by reference.
They're basically cost-free to copy, so you might as well use them by value. Maybe that's usually the case Ultimately, to use fout. Finally, there's no reason to take a bool argument by const-ref. Just take it by value. The first thing you do in the function is open the output file, then double-check that it's open. But that's the last error-checking you do. If there's any problems writing the output after that, they just get forgotten, so this function could return 1 even though the output never got written.
You have multiple options for how to deal with this. That will return 1 if everything worked and all your image data was written to the file you should probably flush it beforehand0 otherwise. If there's an error early in the process, you will waste time spitting bytes into the ether, but no big deal - no harm will be done except time wasted, and the error will be detected.
Another option is to turn exceptions on in your output stream. If any error occurs, output will stop immediately. You can either catch the exception and return 0or let the exception propagate if you prefer. So the next bit is the biggest part of the function. What you do here is set up all your data in local variables That all seems a bit unnecessary. Here's what I recommend instead.
Create a set of functions that write binary values to the output stream. For example.
What you're doing here is that for each row, you're creating a new vector, copying the row data into it, then writing the vector. Why the extra steps? All you really want to do is write the row data. So just write it directly. No need for the extra vector. One thing you might want to do here is some error checking, though.
Creating Bitmap Files from Raw Pixel Data in C++
That's how security disasters like Heartbleed happen.This being the first tutorial I start by explaining the basic concepts of a device context, and how to properly use them. A Device Context is a handle to a drawing surface on some device - Device Contexts can typically be obtained for the display device the entire screenprinters and plotters. Most commonly worked with are window dc's a display DC that merely represents the area of a single window and a memory DC that represents a bitmap as a device.
What these objects all have in common display, printer, bitmap, etc is they have some concept of a "drawing surface" where output will appear. Associated with a Device context a number of tools that can be used to act on the associated drawing surface: Pens, brushes, fonts etc. In the case of physical devices like a plotter there will be a one to onw mapping of HPEN to physical pen. In the case of the display, or memory DC's, a number of preset pens are provided, and more can be created on the fly as needed.
There is another kind of Bitmap called a "Device Independent Bitmap". This type of bitmap is defined in the windows header files as a number of structs that are filled in by the programmer. The tutorial comprises a single window that I create in main. Stored in a global variable is the bitmap handle that is initialized in the OnCreate function, used in OnPaintand destroyed in OnDestroy.
The example bitmap shipped with the tutorial is a color image, and will appear rather flat on a color display. The lack or proper color on color displays will be fixed in tutorial 3 where I intend to discuss palettes. GDI has no built in transparency support - you have to implement transparency in bitmaps yourself.
These methods however are not compatible with other platforms notably Windows 95 and should probably be avoided. GDI supports boolean operations when combinig the contents of DCs surfaces, and we use this to our advantage here.
How to: Create a Bitmap at Run Time
To paint a "transparent" bitmap pair onto a DC the following process is performed:. Also, special care must be taken when using this kind of bitmap with GDI on low color displays: GDI always creates "compatible" DDBs and you the programmer always wants to use "compatible" bitmaps in the format of the display mode.
This can result in a loss of color "resolution" and a whole range of colors might be mapped to the magic transparent color. It is therefore best to make sure that the transparent color is one of the twenty system colors that are guaranteed to always exist. The background "color" of a bitmap is white, and is stored as binary 0. When combined with a color bitmap via a raster operation typically in a call to BitBlt the background pixels in the monochrome bitmap are first mapped to the background color of the color bitmaps DC.
When transferring bytes from a color to a monochrome bitmap, the mapping is simpler. All pixels that are the same color as the background color are mapped to the background color on the mono bitmap 0. All other pixels are demed to be foreground.This post describes a means of taking data in the form of raw pixels containing RGB values as well as the image height, width and the number of bits per pixel 24 in this case and converting this into a bitmap BMP file.
For this example I did not have to worry about padding additional values. Since then I have made some improvements to the original code sample, specifically if the image data happens to be not DWORD-aligned, then a new data array is created and padded such that there will be enough bytes to reach the next DWORD. The original task was to create a one-dimensional array of bytes representing pixel colour data from the two-dimensional adjacency matrix provided.
Each pixel value was then set to black or white, depending on the matrix array value:. This module essentially:. Creates a file handler and writes the file, bitmap info and pixel data into it to create the new bitmap file representation:. Open an input bitmap file 2. Obtain the raw BYTE array, image height and image width from the input bitmap file 3.
Create a new raw BYTE array, which will have space for additional padding if required 4. Save the new raw BYTE array to the new bitmap file. The program extracts the raw data from this and puts it into the buffer, example output of this buffer data:.
It then creates the new BYTE array with any additional padding, if necessary, and the BYTE data is saved as a new bitmap file, as mentioned previously. Here is another example of its usage.
Instead of obtaining raw bitmap data from an existing bitmap file, I create my own bitmap, which in this case is a simple blue square. I then call. Hey, Thank you for sharing this. I was looking to store some results as a bitmap, but having to write the header was putting me off. This code helps explain the header structure a lot. In your case you never actually need to add the padding since your width is so the padding is 0.
However, if you try with other widths, there can be a shift in the byte array on each row, resulting in a degenerate picture. Very useful, and easily pasteable, thanks. I have noticed a small potential bug however. In the save function this line:. BMP image created is distorted if width is not multiple of 4 say if width is How to fix this? This site uses Akismet to reduce spam. Learn how your comment data is processed.A Bitmap is an object used to work with images defined by pixel data.
The following code example demonstrates how to construct a new Bitmap from a file, using the GetPixel and SetPixel methods to recolor the image. It also uses the PixelFormatWidthand Height properties. A bitmap consists of the pixel data for a graphics image and its attributes.
There are many standard formats for saving a bitmap to a file. For more information about supported formats, see Types of Bitmaps.
You can create images from files, streams, and other sources by using one of the Bitmap constructors and save them to a stream or to the file system with the Save method.
Images are drawn to the screen or to memory by using the DrawImage method of the Graphics object. For a list of topics about working with image files, see Working with Images, Bitmaps, Icons, and Metafiles.
The Bitmap class is not accessible across application domains. For example, if you create a dynamic AppDomain and create several brushes, pens, and bitmaps in that domain, then pass these objects back to the main application domain, you can successfully use the pens and brushes.
However, if you call the DrawImage method to draw the marshaled Bitmapyou receive the following exception. Initializes a new instance of the Bitmap class from the specified existing image. Initializes a new instance of the Bitmap class from the specified existing image, scaled to the specified size.
Initializes a new instance of the Bitmap class with the specified size. Initializes a new instance of the Bitmap class with the specified size and with the resolution of the specified Graphics object. Initializes a new instance of the Bitmap class with the specified size, pixel format, and pixel data. Initializes a new instance of the Bitmap class with the specified size and format.
Initializes a new instance of the Bitmap class from the specified data stream. Initializes a new instance of the Bitmap class from the specified file. Initializes a new instance of the Bitmap class from a specified resource. Gets attribute flags for the pixel data of this Image. Gets the height, in pixels, of this Image. Gets the horizontal resolution, in pixels per inch, of this Image. Gets or sets the color palette used for this Image. Gets the pixel format for this Image. Gets IDs of the property items stored in this Image.
Gets all the property items pieces of metadata stored in this Image. Gets the file format of this Image. Gets the vertical resolution, in pixels per inch, of this Image. Gets the width, in pixels, of this Image. Creates an exact copy of this Image. Creates a copy of the section of this Bitmap defined by Rectangle structure and with a specified PixelFormat enumeration. Creates a copy of the section of this Bitmap defined with a specified PixelFormat enumeration. Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.
Releases all resources used by this Image. Releases the unmanaged resources used by the Image and optionally releases the managed resources.