Add greyscale sprite/image push as Alpha channel

[fsender]

Some graphic features require transparency and alpha channels, especially "LGFX_Sprite"
I now need to create a rounded rectangle button with anti aliasing text, solid color borders, and an image background The color of the text and border is the same
I have done a lot of work to ensure the best presentation effect, but I still cannot achieve the best result
Unable to texture the image (such as "LGFX_Sprite") to set transparency using methods such as "pushImage"
If the target is opaque, I can use the "pushImage" method, but the target needs to be presented with a certain degree of transparency
At the same time, it is difficult to present the "LGFX_Sprite" of "Greyscale" in a two-color palette, such as a gradient color from yellow to blue
The "LGFX_Sprite" based on "Greyscale" can be used for rendering anti aliasing fonts (in "*. VLW" format), quickly creating gradients, or anti aliasing graphics
There are only two ways for me to implement this method now:
One: Using the "ARGB8888" format for storage: This will waste a lot of memory and cannot easily and quickly determine the gradient degree through the color of pixels
Secondly, performing pixel by pixel calculations: This will waste a lot of CPU time and make the program run slowly on ESP32xx series chips
Thirdly, use the "readRect" method to read pixels, and then apply anti aliasing techniques to the pixels in this area This will waste time on screen bus communication, even if it occurs in memory, due to the need for repeated conversion and computation of pixel formats
If LovyanGFX natively supports alpha channel format similar to greyscale format, it would be very helpful for my project development
Although it is currently possible to create rectangles using 'fillRectAlpha', this option can only provide monochrome rectangles with transparency
I hope you can:

1. Method for adding "LGFX_Sprite" coloring to greyscale: Set two color parameters to correspond to black and white in the greyscale, respectively
2. Add a method to display greyscale images as Alpha channels on other panels: set a color parameter that corresponds to greyscale white, while greyscale black is considered transparent
3. Add a method to merge and display two equally sized but regular color formatted "LGFX_Sprite" and one greyscale "LGFX_Sprite" on the panel
4. Add a method to split the "LGFX_Sprite" in ARGB8888 format into greyscale "LGFX_Sprite"
5. Develop a greyscale "LGFX_Sprite" anti aliasing method and adapt it to anti aliasing fonts

[fsender]

Now I' m using an argb8888 format sprite and drawing a PNG (with Alpha channel) on it. The func "pushSprite" does not work at all(this sprite was based on my display)

[tobozo]

hi,

The func "pushSprite" does not work

Did sprite.createSprite() even succeed? argb8888 needs a lot of ram e.g. for a 240*240 it needs about ~225KB of contiguous memory; if sprite allocation fails, pushSprite will fail too.

I'm converting this issue to a discussion and will provide additional answers.

[fsender]

After analyzing the memory usage, it is confirmed that the memory allocation for "sprite" is successful, and indeed, the remaining memory has decreased as expected. However, when displaying "argb8888_t" on the panel through the "pushRotateZoom" method, the area where content should be displayed on the screen is either garbled or black. Regardless of whether I use the "spr.pushSprite", "spr.pushRotateZoom", "parent.pushImage(..., spr)", or "parent.pushAlphaImage(..., spr)" methods, it always results in garbled or black screen. The only solution is to use other color formats and specify a certain color as transparent in the last parameter of "spr.pushSprite"
Only when using fillRectAlpha to draw a monochrome rectangle on the parent or directly calling drawPng to draw an PNG image with an alpha channel will it succeed. However, it has no effect on Sprite class.

[tobozo]

If the target is opaque, I can use the "pushImage" method, but the target needs to be presented with a certain degree of transparency.

Provided both source and destination sprites are set to argb8888 using sprite.setColorDepth(32), alpha blending would be achieved using sprite.pushAlphaImage().

[fsender]

My source panel (the LCD) cannot be set as ARGB8888. I'd like to draw something transprent (PNG image, anti-aliased graphic, gradients, etc) on an ARGB8888-formatted sprite, and draw the sprite on my source panel (the LCD or a sprite which does not support Alpha channel). the MCU memory isn't enough for 2 different ARGB8888 sprites.

LGFX ips;
ips.drawPNG("file.png",x,y); //perfect. But cannot add custom options such as rotate any degrees.

LGFX_Sprite spr(&ips);
spr.setColorDepth(16);
spr.createSprite(w,h);
spr.fillScreen(TFT_GREEN);
spr.drawPNG("file.png",0,0);
spr.pushSprite(x,y); //opaque
spr.pushSprite(x,y,TFT_GREEN); //OK, but green edge

LGFX_Sprite spr2(&ips);
spr2.setColorDepth(lgfx::v1::argb8888_4Byte);
spr2.createSprite(w,h);
spr2.drawPNG("file.png",0,0);
spr2.pushSprite(x,y); //opaque
ips.pushAlphaImage(x,y,w,h,reinterpret_cast<lgfx::v1::argb8888_t *>(spr2.getBuffer())); //Black rect
ips.pushAlphaImage(x,y,w,h,reinterpret_cast<lgfx::v1::bgra8888_t *>(spr2.getBuffer())); //Tearing rect
ips.pushImage(x,y,w,h,reinterpret_cast<lgfx::v1::argb8888_t *>(spr2.getBuffer())); //Black rect
ips.pushImage(x,y,w,h,reinterpret_cast<lgfx::v1::bgra8888_t *>(spr2.getBuffer())); //Tearing rect
ips.pushImageRotateZoom(x,y,x0,y0,rotate,zx,zy,w,h,reinterpret_cast<lgfx::v1::argb8888_t *>(spr2.getBuffer())); //Black rect
ips.pushImageRotateZoom(x,y,x0,y0,rotate,zx,zy,w,h,reinterpret_cast<lgfx::v1::bgra8888_t *>(spr2.getBuffer())); //Tearing rect

[tobozo]

My source panel (the LCD) cannot be set as ARGB8888.

does it behave similarly when set to RGB888? e.g. ips.setColorDepth(24);

[fsender]

solved by reading pixels to create an RGB888 buffer then push ARGB8888 sprite on it and push RGB888 buffer on the screen