Vulkan copying image from swap chain - image

Question

I am using the vkCmdCopyImageToBuffer function and getting a memory access violation and don't understand why.
Here is the code:
VkBufferImageCopy region = {};
region.bufferOffset = 0;
region.bufferRowLength = width;
region.bufferImageHeight = height;
region.imageSubresource.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
region.imageSubresource.mipLevel = 0;
region.imageSubresource.baseArrayLayer = 0;
region.imageSubresource.layerCount = 1;
region.imageOffset = { 0, 0, 0 };
region.imageExtent = {
width,
height,
1
};
vkCmdCopyImageToBuffer(m_drawCmdBuffers[i], m_swapChain.buffers[i].image,
VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL, m_renderImage, 1, &region);
The swapchain images are created here in the initialization code:
// Get the swap chain images
images.resize(imageCount);
VK_CHECK_RESULT(fpGetSwapchainImagesKHR(device, swapChain, &imageCount, images.data()));
// Get the swap chain buffers containing the image and imageview
buffers.resize(imageCount);
for (uint32_t i = 0; i < imageCount; i++)
{
VkImageViewCreateInfo colorAttachmentView = {};
colorAttachmentView.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
colorAttachmentView.pNext = NULL;
colorAttachmentView.format = colorFormat;
colorAttachmentView.components = {
VK_COMPONENT_SWIZZLE_R,
VK_COMPONENT_SWIZZLE_G,
VK_COMPONENT_SWIZZLE_B,
VK_COMPONENT_SWIZZLE_A
};
colorAttachmentView.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
colorAttachmentView.subresourceRange.baseMipLevel = 0;
colorAttachmentView.subresourceRange.levelCount = 1;
colorAttachmentView.subresourceRange.baseArrayLayer = 0;
colorAttachmentView.subresourceRange.layerCount = 1;
colorAttachmentView.viewType = VK_IMAGE_VIEW_TYPE_2D;
colorAttachmentView.flags = 0;
buffers[i].image = images[i];
colorAttachmentView.image = buffers[i].image;
VK_CHECK_RESULT(vkCreateImageView(device, &colorAttachmentView, nullptr, &buffers[i].view));
}
And my buffer is similarly created here:
VkBufferCreateInfo createinfo = {};
createinfo.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
createinfo.size = width * height * 4 * sizeof(int8_t);
createinfo.usage = VK_BUFFER_USAGE_TRANSFER_SRC_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;
createinfo.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
//create the image copy buffer
vkCreateBuffer(m_device, &createinfo, NULL, &m_renderImage);
I have tried different pixel formats and different createinfo.usage settings but none help.

Answer 1

VkSurfaceCapabilitiesKHR::supportedUsageFlags defines the limitations on the ways in which you can use the VkImages created by the swap chain. The only one that is guaranteed to be supported is color attachment; all of the other, including transfer src, are optional.
Therefore, you should not assume that you can copy from a presentable image. If you find yourself with a need to do that, you must first query that value. If it does not allow copies, then you must render to your own image, which you copy from. You can render from that image into the presentable one when you intend to present it.