Qt glreadpixels

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Qt glreadpixels

It is very simple to use: Make your class inherit from it and use the subclass like any other QWidgetexcept that you have the choice between using QPainter and standard OpenGL rendering commands.

QOpenGLWidget provides three convenient virtual functions that you can reimplement in your subclass to perform the typical OpenGL tasks:. If you need to trigger a repaint from places other than paintGL a typical example is when using timers to animate scenesyou should call the widget's update function to schedule an update. All rendering happens into an OpenGL framebuffer object. Keep this in mind when creating and binding additional framebuffer objects in the rendering code in paintGL.

Never re-bind the framebuffer with ID 0. Instead, call defaultFramebufferObject to get the ID that should be bound. Just set the requested format via setFormat. Keep in mind however that having multiple QOpenGLWidget instances in the same window requires that they all use the same format, or at least formats that do not make the contexts non-sharable.

This is to ensure that resource sharing between contexts stays functional as all internal contexts are created using the correct version and profile. When performing drawing using QPainter only, it is also possible to perform the painting like it is done for ordinary widgets: by reimplementing paintEvent.

When making OpenGL function calls, it is strongly recommended to avoid calling the functions directly. This way the application will work correctly in all Qt build configurations, including the ones that perform dynamic OpenGL implementation loading which means applications are not directly linking to an GL implementation and thus direct function calls are not feasible.

As for the OpenGL headers, note that in most cases there will be no need to directly include any headers like GL. The OpenGL-related Qt headers will include qopengl. In addition, a copy of the extension headers called glext. These will get included automatically on platforms where feasible. To get a context compatible with a given OpenGL version or profile, or to request depth and stencil buffers, call setFormat :.

With OpenGL 3. As described above, it is simpler and more robust to set the requested format globally so that it applies to all windows and contexts during the lifetime of the application. Below is an example of this:. QOpenGLWidget is intended to be a modern replacement for it. QGLWidget on the other hand uses a native window and surface. The latter causes issues when using it in complex user interfaces since, depending on the platform, such native child widgets may have various limitations, regarding stacking orders for example.Buffer objects are created in the OpenGL server so that the client application can avoid uploading vertices, indices, texture image data, etc every time they are needed.

QOpenGLBuffer performs a shallow copy when objects are copied in this manner, but does not implement copy-on-write semantics. The original object will be affected whenever the copy is modified. Note: QOpenGLBuffer does not implement copy-on-write semantics, so other will be affected whenever the copy is modified. The actual buffer object in the OpenGL server is not created until create is called. Allocates count bytes of space to the buffer, initialized to the contents of data.

Any previous contents will be removed. It is assumed that create has been called on this buffer and that it has been bound to the current context.

See also createreadand write. See also create and write. Binds the buffer associated with this object to the current OpenGL context. Returns false if binding was not possible, usually because type is not supported on this OpenGL implementation. Otherwise, false will be returned from this function. See also release and create. Returns the OpenGL identifier associated with this buffer; zero if the buffer has not been created. Creates the buffer object in the OpenGL server.

Returns true if the object was created; false otherwise. The buffer will be bound to and can only be used in that context or any other context that is shared with it. See also isCreatedallocatewriteand destroy. Destroys this buffer object, including the storage being used in the OpenGL server. All references to the buffer will become invalid.

See also create and destroy.

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Maps the contents of this buffer into the application's memory space and returns a pointer to it. Returns null if memory mapping is not possible. The access parameter indicates the type of access to be performed.

qt glreadpixels

See also unmapcreatebindand mapRange. Maps the range specified by offset and count of the contents of this buffer into the application's memory space and returns a pointer to it. The access parameter specifies a combination of access flags.

See also unmapcreateand bind. Reads the count bytes in this buffer starting at offset into data. Returns true on success; false if reading from the buffer is not supported. See also write and bind. This function must be called with the same QOpenGLContext current as when bind was called on the buffer. This function is a direct call to glBindBuffer type, 0 for use when the caller does not know which QOpenGLBuffer has been bound to the context but wants to make sure that it is released.

Sets the usage pattern for this buffer object to value. This function must be called before allocate or write. See also usagePatternallocateand write. Returns the size of the data in this buffer, for reading operations. Returns -1 if fetching the buffer size is not supported, or the buffer has not been created.Your browser does not seem to support JavaScript.

As a result, your viewing experience will be diminished, and you may not be able to execute some actions. Please download a browser that supports JavaScript, or enable it if it's disabled i. Hi, I have a a huge application initially developped under Qt4.

This application comes with millions of lines to test all parts from low-level basic functions to high-level. Now I have to migrate this application to a Qt5. As QGlWidget still exists, event if it is deprecated, I'm still using this class. So migration of the application was quite simple and works well.

qt glreadpixels

Unfortunately, for regulatory reasons I have to prove this, by running the associated tests. And all tests based on QGLWidget fail. I already spent two days to try to understand the problem.

The failure is on the glReadPixels. It only reads pixels in the area limited by the QWindow. Ans I show the image reduced to the QWindow. I have tried to force the size of the QWindow. In this case the display takes the whole QWidget that is what I want. Any idea of how quickly resolve this stupide problem? If I have to move to QOpenGLWidget, this will take months of developments, that will be an unacceptable cost for my boss.

Alain Can you show:. Hi JKSHtest code is quit simple. The active part other part contains confidential elements is:.

It's not clear: Where is this code being called from? Are you using a widget to update a different widget? Remove the confidential and unnecessary elements, and give us a compilable example including a main function, a simple class, and an output display that demonstrates the problem.This surface can be bound and used as a regular texture in your own OpenGL drawing code. Note that you need to create a QOpenGLFramebufferObject with more than one sample per pixel for primitives to be antialiased when drawing using a QPainter.

For multisample framebuffer objects a color render buffer is created, otherwise a texture with the specified texture target is created. Multiple render targets are also supported, in case the OpenGL implementation supports this. If you want to use a framebuffer object with multisampling enabled as a texture, you first need to copy from it to a regular framebuffer object using QOpenGLContext::blitFramebuffer.

This enum type is used to configure the depth and stencil buffers attached to the framebuffer object when it is created.

Qt Documentation

This enum type is used to configure the behavior related to restoring framebuffer bindings when calling blitFramebuffer. Constructs an OpenGL framebuffer object of the given width and height based on the supplied format.

Constructs an OpenGL framebuffer object of the given size based on the supplied format. Constructs an OpenGL framebuffer object and binds a texture to the buffer of the given width and height.

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See also sizetextureand attachment. Constructs an OpenGL framebuffer object and binds a texture to the buffer of the given size. See also size and texture.

The target parameter is used to specify the OpenGL texture target. By default, no depth and stencil buffers are attached.

glReadPixels not working for the depth-buffer

This behavior can be toggled using one of the overloaded constructors. When internalFormat is not 0it specifies the internal format of the texture or renderbuffer. Note: This is only functional when multiple render targets are supported by the OpenGL implementation. When that is not the case, the function will not add any additional color attachments.

Note: The internal format of the color attachments may differ but there may be limitations on the supported combinations, depending on the drivers.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. 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. This renders correct, but when i resize the window, it scales weird and distorts my shape triangle.

I tried QImage img. Didn't work. Which one is the easiest because i will resize the array when i will resize my window so i want dynamic arrays. I have uploaded a minimal code recreating the bug-weird behaviour in github.

qt glreadpixels

Download and compile using the Qt Creator. Here is how i wanted it works when not resizing. Here is after resizing Weird behaviour.

qt glreadpixels

As you can see, when resizing, the image gets splitted at right and contunues at left at probably another row. So i am guessing the size of the image is wrong needs more width?

By default, the start of each row of an image is assumed to be aligned to 4 bytes. If that is missed, this cause a shift effect at each line of the image, except if the length of a line of the image in bytes is divisible by 4.

Learn more. Asked 8 months ago.

Qt Documentation

Active 8 months ago. Viewed times. What i tried I tried QImage img. Some code I have uploaded a minimal code recreating the bug-weird behaviour in github. Rabbid76 Active Oldest Votes. Rabbid76 Rabbid76 However, if i resize too much, it cuts the triangle, horizontally if i resize that way, and vertically if the other way. Please, check my code on github to see the problem.

Well i figured it out. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

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Post as a guest Name. Email Required, but never shown. The Overflow Blog. Q2 Community Roadmap.OpenGL ES 2. However, it can be difficult to use the functions from that subset because they need to be resolved manually on desktop systems. This is somewhat faster than the previous approach due to avoiding the creation of a new instance, but the difference is fairly small since the internal data structures are shared, and function resolving happens only once for a given context, regardless of the number of QOpenGLFunctions instances initialized for it.

While such functions, for example glClear or glDrawArrayscan be called also directly, as long as the application links to the platform-specific OpenGL library, calling them via QOpenGLFunctions enables the possibility of dynamically loading the OpenGL implementation. For example, the following checks if non power of two textures are available:. Constructs a function resolver for context. An object constructed in this way can only be used with context and other contexts that share with it. Use initializeOpenGLFunctions to change the object's context association.

See also initializeOpenGLFunctions. Constructs a default function resolver.

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The resolver cannot be used until initializeOpenGLFunctions is called to specify the context. Convenience function that calls glBlendColor redgreenbluealpha. Convenience function that calls glBufferData targetsizedatausage.

Convenience function that calls glBufferSubData targetoffsetsizedata. Convenience function that calls glClearColor redgreenbluealpha. Convenience function that calls glColorMask redgreenbluealpha. Convenience function that calls glCompressedTexImage2D targetlevelinternalformatwidthheightborderimageSizedata. Convenience function that calls glCompressedTexSubImage2D targetlevelxoffsetyoffsetwidthheightformatimageSizedata.

Convenience function that calls glCopyTexImage2D targetlevelinternalformatxywidthheightborder. Convenience function that calls glCopyTexSubImage2D targetlevelxoffsetyoffsetxywidthheight. Convenience function that calls glDrawElements modecounttypeindices. Convenience function that calls glFramebufferRenderbuffer targetattachmentrenderbuffertargetrenderbuffer. Convenience function that calls glFramebufferTexture2D targetattachmenttextargettexturelevel. Convenience function that calls glGetActiveAttrib programindexbufsizelengthsizetypename.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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.

This renders correct, but when i resize the window, it scales weird and distorts my shape triangle. I tried QImage img. Didn't work. Which one is the easiest because i will resize the array when i will resize my window so i want dynamic arrays. I have uploaded a minimal code recreating the bug-weird behaviour in github. Download and compile using the Qt Creator. Here is how i wanted it works when not resizing.

Here is after resizing Weird behaviour. As you can see, when resizing, the image gets splitted at right and contunues at left at probably another row.

So i am guessing the size of the image is wrong needs more width? By default, the start of each row of an image is assumed to be aligned to 4 bytes. If that is missed, this cause a shift effect at each line of the image, except if the length of a line of the image in bytes is divisible by 4. Learn more. Asked 8 months ago. Active 8 months ago.

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Viewed times. What i tried I tried QImage img. Some code I have uploaded a minimal code recreating the bug-weird behaviour in github. Rabbid76 Active Oldest Votes. Rabbid76 Rabbid76


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