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OpenGLFrameBuffer: Add a row order parameter for reading and writing pixels

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This also fixes a bug where saving and restoring the framebuffer state
could unexpectedly apply a vertical flip to the buffer content.
This commit is contained in:
reuk 2025-07-10 12:36:11 +01:00
parent c77e8a73cc
commit f5a6c510c0
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4 changed files with 74 additions and 18 deletions
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39
modules/juce_opengl/opengl/juce_OpenGLFrameBuffer.cpp
View file

@ -58,6 +58,8 @@ public:
{
int width = 0, height = 0;
std::vector<PixelARGB> data;
static constexpr auto order = RowOrder::fromBottomUp;
};
~Pimpl() override
@ -97,7 +99,7 @@ public:
Image::BitmapData bitmap (image, Image::BitmapData::readOnly);
return initialise (context, bitmap.width, bitmap.height)
&& writePixels ((const PixelARGB*) bitmap.data, image.getBounds());
&& writePixels ((const PixelARGB*) bitmap.data, image.getBounds(), RowOrder::fromTopDown);
}
bool initialise (OpenGLFrameBuffer& other)
@ -233,7 +235,7 @@ public:
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
}
bool readPixels (PixelARGB* target, const Rectangle<int>& area)
bool readPixels (PixelARGB* target, const Rectangle<int>& area, RowOrder order)
{
auto* transientState = makeAndGetCurrentRenderingTarget();
@ -246,10 +248,25 @@ public:
glReadPixels (area.getX(), area.getY(), area.getWidth(), area.getHeight(),
JUCE_RGBA_FORMAT, GL_UNSIGNED_BYTE, target);
if (order == RowOrder::fromTopDown)
{
auto* end = target + area.getWidth() * area.getHeight();
for (auto y = 0; y < area.getHeight() / 2; ++y)
{
const auto offset = area.getWidth() * y;
auto* rowA = target + offset;
auto* rowB = end - offset - area.getWidth();
for (auto x = 0; x < area.getWidth(); ++x)
std::swap (rowA[x], rowB[x]);
}
}
return true;
}
bool writePixels (const PixelARGB* data, const Rectangle<int>& area)
bool writePixels (const PixelARGB* data, const Rectangle<int>& area, RowOrder order)
{
if (associatedContext == nullptr)
return false;
@ -275,7 +292,7 @@ public:
tex.getHeight()),
transientState->width,
transientState->height,
true,
order == RowOrder::fromTopDown,
false);
JUCE_CHECK_OPENGL_ERROR
@ -422,7 +439,9 @@ private:
if (! initialise (context, savedState.width, savedState.height))
return false;
writePixels (savedState.data.data(), Rectangle (savedState.width, savedState.height));
writePixels (savedState.data.data(),
Rectangle (savedState.width, savedState.height),
SavedState::order);
return true;
}
@ -432,7 +451,7 @@ private:
area.getHeight(),
std::vector<PixelARGB> ((size_t) area.getWidth() * (size_t) area.getHeight()) };
if (! readPixels (result.data.data(), area))
if (! readPixels (result.data.data(), area, SavedState::order))
return {};
return result;
@ -551,14 +570,14 @@ void OpenGLFrameBuffer::makeCurrentAndClear()
pimpl->makeCurrentAndClear();
}
bool OpenGLFrameBuffer::readPixels (PixelARGB* targetData, const Rectangle<int>& sourceArea)
bool OpenGLFrameBuffer::readPixels (PixelARGB* targetData, const Rectangle<int>& sourceArea, RowOrder order)
{
return pimpl->readPixels (targetData, sourceArea);
return pimpl->readPixels (targetData, sourceArea, order);
}
bool OpenGLFrameBuffer::writePixels (const PixelARGB* srcData, const Rectangle<int>& targetArea)
bool OpenGLFrameBuffer::writePixels (const PixelARGB* srcData, const Rectangle<int>& targetArea, RowOrder order)
{
return pimpl->writePixels (srcData, targetArea);
return pimpl->writePixels (srcData, targetArea, order);
}
GLuint OpenGLFrameBuffer::getCurrentFrameBufferTarget() noexcept

19
modules/juce_opengl/opengl/juce_OpenGLFrameBuffer.h
View file

@ -116,17 +116,24 @@ public:
/** Selects the framebuffer as the current target, and clears it to transparent. */
void makeCurrentAndClear();
enum class RowOrder
{
fromBottomUp, //< Standard order for OpenGL, the bottom-most row of pixels is first.
//< Using this pixel ordering may be faster, but may be incompatible
//< with other JUCE functions that operate on image pixel data, as these
//< generally expect the rows to be ordered top-down.
fromTopDown, //< Standard order for JUCE images, the top-most row of pixels is first.
};
/** Reads an area of pixels from the framebuffer into a 32-bit ARGB pixel array.
The lineStride is measured as a number of pixels, not bytes - pass a stride
of 0 to indicate a packed array.
The RowOrder parameter specifies the order of rows in the resulting array.
*/
bool readPixels (PixelARGB* targetData, const Rectangle<int>& sourceArea);
bool readPixels (PixelARGB* targetData, const Rectangle<int>& sourceArea, RowOrder);
/** Writes an area of pixels into the framebuffer from a specified pixel array.
The lineStride is measured as a number of pixels, not bytes - pass a stride
of 0 to indicate a packed array.
The RowOrder parameter specifies the order of rows in srcData.
*/
bool writePixels (const PixelARGB* srcData, const Rectangle<int>& targetArea);
bool writePixels (const PixelARGB* srcData, const Rectangle<int>& targetArea, RowOrder);
private:
class Pimpl;

6
modules/juce_opengl/opengl/juce_OpenGLImage.cpp
View file

@ -116,13 +116,13 @@ private:
mode (modeIn)
{
if (mode != Image::BitmapData::writeOnly)
self->frameBuffer.readPixels (data.get(), getArea());
self->frameBuffer.readPixels (data.get(), getArea(), order);
}
~DataReleaser() override
{
if (mode != Image::BitmapData::readOnly)
self->frameBuffer.writePixels (data, getArea());
self->frameBuffer.writePixels (data, getArea(), order);
}
Rectangle<int> getArea() const
@ -134,6 +134,8 @@ private:
HeapBlock<PixelARGB> data;
Rectangle<int> area;
Image::BitmapData::ReadWriteMode mode;
static constexpr auto order = OpenGLFrameBuffer::RowOrder::fromBottomUp;
};
JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (OpenGLFrameBufferImage)