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add ability to retrieve a golang color.Palette from a given video format

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This commit is contained in:
tinyzimmer
2020-10-08 08:42:27 +03:00
parent 52a3ef35e1
commit 8b72e74561
3 changed files with 276 additions and 127 deletions
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40
examples/appsrc/main.go
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@@ -41,7 +41,7 @@ func createPipeline() (*gst.Pipeline, error) {
// Specify the format we want to provide as application into the pipeline
// by creating a video info with the given format and creating caps from it for the appsrc element.
videoInfo := video.NewInfo().
WithFormat(video.FormatRGBx, width, height).
WithFormat(video.FormatRGBA, width, height).
WithFPS(gst.Fraction(2, 1))
src.SetCaps(videoInfo.ToCaps())
@@ -50,6 +50,9 @@ func createPipeline() (*gst.Pipeline, error) {
// Initialize a frame counter
var i int
// Get all 256 colors in the RGB8P palette.
palette := video.FormatRGB8P.Palette()
// Since our appsrc element operates in pull mode (it asks us to provide data),
// we add a handler for the need-data callback and provide new data from there.
// In our case, we told gstreamer that we do 2 frames per second. While the
@@ -58,23 +61,25 @@ func createPipeline() (*gst.Pipeline, error) {
// this handler will be called (on average) twice per second.
src.SetCallbacks(&app.SourceCallbacks{
NeedDataFunc: func(self *app.Source, _ uint) {
if i == 100 {
// If we've reached the end of the palette, end the stream.
if i == len(palette) {
src.EndStream()
return
}
fmt.Println("Producing frame:", i)
// Produce an image frame for this iteration.
pixels := produceImageFrame(i)
// Create a buffer that can hold exactly one video RGBx frame.
// Create a buffer that can hold exactly one video RGBA frame.
buf := gst.NewBufferWithSize(videoInfo.Size())
// For each frame we produce, we set the timestamp when it should be displayed
// The autovideosink will use this information to display the frame at the right time.
buf.SetPresentationTimestamp(time.Duration(i) * 500 * time.Millisecond)
// Produce an image frame for this iteration.
pixels := produceImageFrame(palette[i])
// At this point, buffer is only a reference to an existing memory region somewhere.
// When we want to access its content, we have to map it while requesting the required
// mode of access (read, read/write).
@@ -94,12 +99,11 @@ func createPipeline() (*gst.Pipeline, error) {
return pipeline, nil
}
func produceImageFrame(i int) []uint8 {
func produceImageFrame(c color.Color) []uint8 {
upLeft := image.Point{0, 0}
lowRight := image.Point{width, height}
img := image.NewRGBA(image.Rectangle{upLeft, lowRight})
c := getColor(i)
for x := 0; x < width; x++ {
for y := 0; y < height; y++ {
img.Set(x, y, c)
@@ -109,26 +113,6 @@ func produceImageFrame(i int) []uint8 {
return img.Pix
}
func getColor(i int) color.Color {
color := color.RGBA{}
if i%2 == 0 {
color.R = 0
} else {
color.R = 255
}
if i%3 == 0 {
color.G = 0
} else {
color.G = 255
}
if i%5 == 0 {
color.B = 0
} else {
color.B = 255
}
return color
}
func handleMessage(msg *gst.Message) error {
defer msg.Unref() // Messages are a good candidate for trying out runtime finalizers